Multi Light Usage
Using more than one light for studio work involves placing the lights in relationship not only to the subject, but to each other as well. The relationship of lights not only depends on the physical placement, but also the power output, modifiers used, temperature of light, and more interactions than could be covered in several books. For the purpose of this class, we will be working with lights of the same temperature and dealing primarily with power, placement and modifiers.
How Does Light Work
The main thing to remember when using multiple lights (single light as well) is how light works. Light can only travel in a straight line. It does not bend. Light can be redirected easily though. Light can be filtered for a specific color; once this is done it cannot be undone. Light is made up of countless individual rays of light that cannot be seen individually by us, only as a whole. Light is not a big solid beam, but can be made to look that way.
The difference between direct light and diffused light is not a softening of the light; light cannot be softened, only redirected. What we call soft or diffused light is actually light that has been scattered. The light is still traveling in a straight line, but there are now countless rays being directed in every angle imaginable instead of in a more direct path. This randomness of light paths is what fills in areas more evenly and appears to wrap itself around a subject. It reality it isn’t, the extreme range of angles the light is now traveling in has a much better chance of hitting the subject in different places. The further you travel away from a diffused light source, the more it will become a point light source and the more a shadow will become apparent.
Using modifiers to redirect light (reflectors, diffusers, gobos, barn doors, grinds, snoots etc…)
Keep this all in mind when placing your lights. Straight line of light will determine shadow direction and diffusion of light source combined with proximity will determine shadow intensity.
Lighting Ratios
Lighting ratios are the main concern when working with two or more lights. The term refers to the ratio of light being put out by one source in relation to another. The ratio is always referred to with the first number being the main (usually the most powerful) light and the second being the fill. The main will always be the number “1” in the equation and the second number being how many stops less +1 the other light is putting out that is reaching the subject. So, a 1:2 ratio will have the main light at full with the fill light having 1 less stop or ½ the power so 1+ 1 (stop less) will give you the 2 in 1:2.
The ratio does not have anything to do with actual power being output from the source. It has to do with the amount of light making it to the subject. Two lights set at the same output levels, but at different distances away from the subject will not have a 1:1 ratio even though they’re putting out the same amount of power. The same applies to lights using different modifiers that can affect the amount of light hitting the subject.
The exception to the rule is if you see a ratio that says something like 3:1. The number 1 still refers to the main light, which is what you are metering for, but the higher first number refers to a light that is being used to overexpose an area. An example would be for a high key shot where you need to ever expose the background in order to blow it out for effect. The stronger lights would then pointed directly at the background, pulling the subject further out to avoid spillover onto the subject from the background lights and allowing the exposure from the main to be unaffected.
Categories of Lights
Main: The main light is just that, it’s the light that produces the light that is used for the exposure of the subject and is the one that is metered for exposure value. It is not always the most powerful light being used. It is always the light that produces the exposure value that will be set on the camera.
Fill: The fill light is the light (or lights) that is used to fill in an area on the subject that is in need of extra light hitting it. This normally means the shadow area opposite from the main, but not always. The fill might also be from a shorter angle to add to the main or from the side to fill more along the edge. The fill will always be a smaller exposure value than the main.
Hair Light: The hair light is hung above the subject and is used to create a smooth highlight along the edge of the hair to give it more separation from the background. The angle it is set in relation to the subject will determine the amount of highlight created. An angle from further back will have a thinner line, straight above will produce a broader line and in front will light the hair fully, but will also have spill off onto the face most likely. You can use a snoot to direct the hair light more accurately, but this will also create a more focused highlight and the exposure value will increase.
Kicker: the kicker light is a small powerful light that is directed to a specific area to really boost the exposure value of it. It is usually directed upwards, but can also be straight or downwards also. The kicker light might have (and usually does) a higher exposure value than the main. This is normally used in fashion photography, so use it to get that look. The light from the kicker should be minimal on the area it is hitting on the subject. Do not over power a subject with the kicker.
Background Light: The purpose of the background light is to provide illumination to the background. It is normally placed behind the subject directed up toward the backdrop. This will give a brighter area behind the subject with a falloff to the edges of the image. Altering the angle and distance of the light in relation to the backdrop will give different effects for it. Closer will produce a brighter area behind the subject with a faster falloff; farther away will give you a softer more gradual falloff. When lighting for a high key situation, then the background light will be set at a higher metered value than the main.
Backlight: Do not confuse with background light. A backlight is used to light the subject from behind and is aimed toward the camera, not the background. The effect you would be going for is edge lighting around the subject. This is mostly visible on someone with lots of hair that is thick.
Metering
When metering for multiple lights, first decide which light is to be the main for exposure. Set that light and take a meter reading for it with no other lights on. Now place the fill light, turn off the main and meter for it. The meter reading should be less than it was for the main. How much less is determined by what the final image result you want is.
If you’re using a back ground light, place it and again meter from the spot that will be centered in the image toward the camera. It should be over, under, or the same as the main all-depending on what the look you are going for is.
If using a kicker…. Turn off the other lights and now meter the kicker as placed in relation to the subject, meter toward the spot where the kicker will hit. It should be slightly over the reading for the main light. How much over is again determined by the effect you are looking for.
Using a Backlight…Meter the light as if the camera will be directly behind the light instead of being in front of the subject who is in front of the light. So, meter toward the background. The reason is to get an accurate measure of the light that will be illuminating the edges of your subject. Light should be over the main if you want a hard “electrical” halo effect. Less if you want a slight differential from the background that is not overpowering.
Sunday, May 16, 2010
Sunday, May 9, 2010
Lighting 1
What is Lighting
Photography is ALL about the lighting. Without it, there is no picture taking. Using studio lighting is about controlling the way the light plays across the subject matter to create the image you want. In order to do this the photographer will employ a wide variety of tools to control and create the mixture of light and shadow needed. Incredibly large amount of books have been written about lighting, and it takes years to fully understand it, if ever. This is a short synopsis of general studio lighting usage.
Single Light Usage
Types of Studio Lights
Continuous Source: A light that has a high wattage output. It’s used for lighting a subject for exposure using only the light generated by the source.
Advantages: What you see is what you get. There is no guessing how the light will fall, you see it as is. Easier to control with modifiers such as gobos and barn doors.
Disadvantages: You will be exposing your subjects to very bright lights for the duration of the shoot. Some people are uncomfortable with that. Also, the iris of the eyes will close up, it is considered more attractive for the iris to be dilated. Also, generates a lot of heat. Subjects could be sweating soon. There are newer fluorescent light banks out that don’t produce the heat. Still have the bright lights to deal with and the price ( $2,500 plus)
Strobe or Flash: Most standard lighting used for studio work. Unit consists of a modeling light to show general placement of lighting and a flash or strobe tube that goes off when picture is taken for full lighting power.
Advantages: Most mobile of the lighting. Wide range of modifiers available. Does not heat up a studio as fast. Helps keep the iris of the eye dilated.
Disadvantages: Some guess work on how the final light will be falling. Bright flashes can be frightening to some children. Harder to control with some modifiers such as gobos and barn doors.
Light Modifiers
Light modifiers are used to change the way your source light hits the subject. This can be diffusion, blocking, directing, bouncing, or any other method that alters the path of light. Unmodified light is called direct lighting, or bare bulb.
Basic Light Modifiers
Umbrellas: Umbrellas can be either a reflective or shoot through style. The reflective style will have the light facing away from the subject with the umbrella being used to bounce the light back toward the subject. This will disperse the light creating a larger point source which will decrease the shadows more than a smaller point source. The shoot through umbrellas also diffuse the light, but with a more dramatic falloff toward the edges of the image.
Soft Box: Soft boxes wrap around the light source, bounce the light all around and then direct it out of a frosted diffusion material to create an even soft light. Soft boxes come in different sizes from rather small to large enough to cover an entire car with continuous light. One thing to keep in mind with a softbox is that the closer the light is to the subject, the more the light will wrap around the subject.
Honey Combs: Honey combs are made to fit onto the front of a softbox or other modifiers and create a more directionalized light source. This reduces spill off of light onto areas you might not want them to be on, like the background or a different part of the subject. They are made with different degrees of direction. A zero degree honey comb will give you a straight line light source while a fifteen degree one will produce a light source with a fifteen degree spread.
Barn Doors: Barn doors are just like they sound. It’s a door, or strip of fabric, that is used to cover an area of the light source to keep light from hitting the subject except for where it’s open. If you want to have a small area receive light, like just the face, you would use a barn door to minimize the amount of light to the area you want to light up. More effective when used in tandem with a honey comb situation.
Gobo: A Gobo is a device that is used to cast a shadow onto the subject. The difference between a barn door and gobo is that the barn door doesn’t allow light out, the gobo produces a shadow with the characteristics of a shadow. You get a gradual fall off of light instead of a more direct line of not lighting. Gobos can be any shape and size depending on what you want to accomplish. Some are held into place with a stand and clamps, other times an assistant will hold them.
Reflectors: Reflectors are used to bounce light back in the direction it came from, for the most part. They are made from highly reflective material (usually metallic in nature) and will slightly disperse the light as it is reflected. The thing to remember about reflectors (hence “for the most part”) is that angle of incidence equal angle of reflection. So, if light is hitting the reflector at 45 degrees, then the light will not bounce straight back the way it cam, but will bounce off at 45 degrees in the opposite direction. If you want to fill the shadow under a chin, then place the main light above and behind you toward the subject, then place the reflector under the subject almost straight up and in front. Have the reflector placed so that the light hitting it at the angle is now bounced up toward the subject at the same angle as the light, just from below. If you angle the reflector toward the subject, then light from the source will not be able to hit it and bounce up. Angles are the most critical thing to pay attention to when using a reflector.
Snoot: A snoot is basically a tube that is placed over the light source to create a highly directionalized beam with exceedingly small spill. You need to completely cover the source and then reduce the diameter of the tube to what you want. It is better to have a funnel shape leading off to a tube instead of just ending at the end of the funnel. The longer the tube, the less spread of the light. It is very useful to use as a hair light.
Law of Inverse Proportions: One of the easiest ways to control the amount of light hitting the subject is to simply move the light source further away from it. As light spreads out, there is the same amount to use at all times, the difference is the area it has to now cover. If you have an exposure of f8 with the light 5 feet away, when you move the light to 10 feet away the exposure will now be f5.6. The rule states that each time you double the distance the light now has four times the amount of area to cover, which will result in a 1 stop increase in exposure to compensate. The same is true in reverse. Half the distance equals a one stop decrease in exposure value. This rule is not very precise when used with a directional light source.
Basic One Light Setups
Butterfly: Most commonly used. Light is set up over photographer angled down toward subject creating a minimum shadow just under the nose. Sometimes referred to as a nose line light. Catch light will be centered toward the top of the eye. Does not create much depth for the face. Easiest to use with multiple subjects since shadows from each will fall downward behind them.
Rembrandt: Also called ¾ lighting. Named for the style of lighting Rembrandt used in his work. Light is slightly above and to the side of subject. There will be a shadow falling on the unlit side of the face. A sure sign of this lighting is a small triangle of light directly under the eye on the darker side created by the shadow form the nose and cheek. This lighting will give more depth to a face, careful positioning is needed to keep the dark side eye from getting lost in shadow.
Rim: Light is directed more toward the camera than the subject. Basically you are lighting for the side of the subject that is away from the camera. This is used primarily with profile shots where you want to emphasize the lines of the subject for effect.
Back Lighting: You place a light facing directly at the camera, and then place the subject between the two. Strictly for silhouette shots.
Flat Lighting: The most basic lighting there is. Light is directly above the lens pointed straight at the subject. Called flat because the light hits the subject flat on, no shadows, no contours or depth to subject. This is what you get from a direct on camera flash. Shadow will be directly behind the subject in an outline form. Multi subject close together will have a hard line shadow on them. Try to avoid this lighting if at all possible, it is the most unflattering.
Broad Lighting: Broad lighting is lighting the subject in order to minimize shadow. Most widely used in fashion, glamour and commercial photography. The idea is to illuminate everything and bring out the details with minimum shadowing to maintain depth. Light is almost directly in front of subject and slightly up, a reflector is usually placed under the chin to fill in shadows.
Short Lighting: Most people will benefit from a degree of short lighting. Short lighting is used at more of an angle in order to create more shadow fall off as the subject recedes away form the camera. This will have a slimming effect on people. The degree of short lighting can vary from minimal to more extreme. Judgment is needed in order to decide how much is needed for the particular situation. The light will be at an angle in relationship to the subject and camera. The higher the angle the more short it will be. There is no specific angle to place the lighting since the degree is determined by just how much shadow you want to create.
Metering
One of the most difficult things to do can be metering a lighting setup. An overexposed image can result in lost of detail in the highlights, an under exposed image will suffer in shadow detail. Add into the mix the mood you’re trying to set. Is it a bright open image or a dark moody photo? Same lighting with different exposure can be used for both sometimes.
So, how do you meter? A hand held meter with a diffusion bulb on front of the sensor is best. A light meter will read for your exposure as an 18% gray reflective surface, which is pretty close for skin tones. Keeping this in mind, hold the meter pointing toward the camera lens (or where it will be) not toward the light. You want to measure the amount of light that will be bouncing toward the camera, not the amount being generated total. If you are shooting a rim lighting shot, pointing the meter toward the camera will give you a way overexposed reading. The reason being is that you are now metering for the shadow portion of the image instead of the area you want to expose for. In this situation, meter in the direction the subject will be facing.
The idea for metering is to measure the exposure value of the brightest part of the image as the light will be hitting it. Keep this in mind when deciding what you want the exposure to be for. For a high key set up the meter will be for the subject, not the background. For a low key shot, the metering should be for the very small portion that is getting hit by the light. So, for rim lighting (a low key shot) it will be the ridge of the subject. Since the light will be playing across a very small portion of the area visible to the camera, then measure the side that is away form the camera that will be getting the full value and expose for that since the value will be the same for the small part you will be photographing.
If you are shooting a backlit subject for a silhouette, then measure the light directly instead of toward the camera. You will want the subject to go completely black with the exposure being for background giving it the contrast needed. Meter accordingly.
Most meters are designed to measure a strobe exposure at the ideal setting for the camera sync. Dragging the shutter will change the exposure value by allowing more ambient light to enter in. Keep this in mind when setting the camera. You might have to stop the camera down a bit to compensate.
Meters are pretty well calibrated straight from the factory. Still, they should be tested by shooting. Meter the setup, and then bracket the frames without anything moving. Look at the uncorrected images (or negatives) and determine where the exposure should be. If the image exposes better at a different setting than the meter registered, then adjust the meter to read accordingly. If shooting digital, use the histogram to determine the exposure of the scene and if it’s under or over. DO NOT JUDGE IT BY THE SCREEN IMAGE, THEY ARE NOT CALIBRATED. USE THE HISTOGRAM, NUMBERS DON’T LIE!!!
Some Tech Terms
Ambient Light: Light that is naturally available and usually not controllable. The model lights in the strobes is an ambient light source as is window lighting or any other source outside of what is being used for the lighting setup.
Fall Off: Fall off is the decreasing intensity of the light as it moves further away from the subject or beyond the edge that the light has been directed. It is most noticeable at times around the edges of a wider angled shot that shows up as a vignette.
Spill Light: Spill is the light that affects part of the image that you did not want it too. An example would be if you were lighting a subject for a low key or rim lighting, the light that strays onto the background (which you didn’t want to) is the spill off light from your main light source. It is controlled with a honey comb or barn doors.
Dragging the Shutter: Sometimes it is advantageous to make an exposure longer than the recommended flash sync of the camera. The reason for doing this is to allow more ambient light into the exposure. This will give a slight blurring in the studio along with a color shift from the modeling lights. Doing this can cerate a slightly smoother and warmer skin tone. Another reason would be on location in order to bring the background exposure into alignment with the foreground that was hit by the flash.
Photography is ALL about the lighting. Without it, there is no picture taking. Using studio lighting is about controlling the way the light plays across the subject matter to create the image you want. In order to do this the photographer will employ a wide variety of tools to control and create the mixture of light and shadow needed. Incredibly large amount of books have been written about lighting, and it takes years to fully understand it, if ever. This is a short synopsis of general studio lighting usage.
Single Light Usage
Types of Studio Lights
Continuous Source: A light that has a high wattage output. It’s used for lighting a subject for exposure using only the light generated by the source.
Advantages: What you see is what you get. There is no guessing how the light will fall, you see it as is. Easier to control with modifiers such as gobos and barn doors.
Disadvantages: You will be exposing your subjects to very bright lights for the duration of the shoot. Some people are uncomfortable with that. Also, the iris of the eyes will close up, it is considered more attractive for the iris to be dilated. Also, generates a lot of heat. Subjects could be sweating soon. There are newer fluorescent light banks out that don’t produce the heat. Still have the bright lights to deal with and the price ( $2,500 plus)
Strobe or Flash: Most standard lighting used for studio work. Unit consists of a modeling light to show general placement of lighting and a flash or strobe tube that goes off when picture is taken for full lighting power.
Advantages: Most mobile of the lighting. Wide range of modifiers available. Does not heat up a studio as fast. Helps keep the iris of the eye dilated.
Disadvantages: Some guess work on how the final light will be falling. Bright flashes can be frightening to some children. Harder to control with some modifiers such as gobos and barn doors.
Light Modifiers
Light modifiers are used to change the way your source light hits the subject. This can be diffusion, blocking, directing, bouncing, or any other method that alters the path of light. Unmodified light is called direct lighting, or bare bulb.
Basic Light Modifiers
Umbrellas: Umbrellas can be either a reflective or shoot through style. The reflective style will have the light facing away from the subject with the umbrella being used to bounce the light back toward the subject. This will disperse the light creating a larger point source which will decrease the shadows more than a smaller point source. The shoot through umbrellas also diffuse the light, but with a more dramatic falloff toward the edges of the image.
Soft Box: Soft boxes wrap around the light source, bounce the light all around and then direct it out of a frosted diffusion material to create an even soft light. Soft boxes come in different sizes from rather small to large enough to cover an entire car with continuous light. One thing to keep in mind with a softbox is that the closer the light is to the subject, the more the light will wrap around the subject.
Honey Combs: Honey combs are made to fit onto the front of a softbox or other modifiers and create a more directionalized light source. This reduces spill off of light onto areas you might not want them to be on, like the background or a different part of the subject. They are made with different degrees of direction. A zero degree honey comb will give you a straight line light source while a fifteen degree one will produce a light source with a fifteen degree spread.
Barn Doors: Barn doors are just like they sound. It’s a door, or strip of fabric, that is used to cover an area of the light source to keep light from hitting the subject except for where it’s open. If you want to have a small area receive light, like just the face, you would use a barn door to minimize the amount of light to the area you want to light up. More effective when used in tandem with a honey comb situation.
Gobo: A Gobo is a device that is used to cast a shadow onto the subject. The difference between a barn door and gobo is that the barn door doesn’t allow light out, the gobo produces a shadow with the characteristics of a shadow. You get a gradual fall off of light instead of a more direct line of not lighting. Gobos can be any shape and size depending on what you want to accomplish. Some are held into place with a stand and clamps, other times an assistant will hold them.
Reflectors: Reflectors are used to bounce light back in the direction it came from, for the most part. They are made from highly reflective material (usually metallic in nature) and will slightly disperse the light as it is reflected. The thing to remember about reflectors (hence “for the most part”) is that angle of incidence equal angle of reflection. So, if light is hitting the reflector at 45 degrees, then the light will not bounce straight back the way it cam, but will bounce off at 45 degrees in the opposite direction. If you want to fill the shadow under a chin, then place the main light above and behind you toward the subject, then place the reflector under the subject almost straight up and in front. Have the reflector placed so that the light hitting it at the angle is now bounced up toward the subject at the same angle as the light, just from below. If you angle the reflector toward the subject, then light from the source will not be able to hit it and bounce up. Angles are the most critical thing to pay attention to when using a reflector.
Snoot: A snoot is basically a tube that is placed over the light source to create a highly directionalized beam with exceedingly small spill. You need to completely cover the source and then reduce the diameter of the tube to what you want. It is better to have a funnel shape leading off to a tube instead of just ending at the end of the funnel. The longer the tube, the less spread of the light. It is very useful to use as a hair light.
Law of Inverse Proportions: One of the easiest ways to control the amount of light hitting the subject is to simply move the light source further away from it. As light spreads out, there is the same amount to use at all times, the difference is the area it has to now cover. If you have an exposure of f8 with the light 5 feet away, when you move the light to 10 feet away the exposure will now be f5.6. The rule states that each time you double the distance the light now has four times the amount of area to cover, which will result in a 1 stop increase in exposure to compensate. The same is true in reverse. Half the distance equals a one stop decrease in exposure value. This rule is not very precise when used with a directional light source.
Basic One Light Setups
Butterfly: Most commonly used. Light is set up over photographer angled down toward subject creating a minimum shadow just under the nose. Sometimes referred to as a nose line light. Catch light will be centered toward the top of the eye. Does not create much depth for the face. Easiest to use with multiple subjects since shadows from each will fall downward behind them.
Rembrandt: Also called ¾ lighting. Named for the style of lighting Rembrandt used in his work. Light is slightly above and to the side of subject. There will be a shadow falling on the unlit side of the face. A sure sign of this lighting is a small triangle of light directly under the eye on the darker side created by the shadow form the nose and cheek. This lighting will give more depth to a face, careful positioning is needed to keep the dark side eye from getting lost in shadow.
Rim: Light is directed more toward the camera than the subject. Basically you are lighting for the side of the subject that is away from the camera. This is used primarily with profile shots where you want to emphasize the lines of the subject for effect.
Back Lighting: You place a light facing directly at the camera, and then place the subject between the two. Strictly for silhouette shots.
Flat Lighting: The most basic lighting there is. Light is directly above the lens pointed straight at the subject. Called flat because the light hits the subject flat on, no shadows, no contours or depth to subject. This is what you get from a direct on camera flash. Shadow will be directly behind the subject in an outline form. Multi subject close together will have a hard line shadow on them. Try to avoid this lighting if at all possible, it is the most unflattering.
Broad Lighting: Broad lighting is lighting the subject in order to minimize shadow. Most widely used in fashion, glamour and commercial photography. The idea is to illuminate everything and bring out the details with minimum shadowing to maintain depth. Light is almost directly in front of subject and slightly up, a reflector is usually placed under the chin to fill in shadows.
Short Lighting: Most people will benefit from a degree of short lighting. Short lighting is used at more of an angle in order to create more shadow fall off as the subject recedes away form the camera. This will have a slimming effect on people. The degree of short lighting can vary from minimal to more extreme. Judgment is needed in order to decide how much is needed for the particular situation. The light will be at an angle in relationship to the subject and camera. The higher the angle the more short it will be. There is no specific angle to place the lighting since the degree is determined by just how much shadow you want to create.
Metering
One of the most difficult things to do can be metering a lighting setup. An overexposed image can result in lost of detail in the highlights, an under exposed image will suffer in shadow detail. Add into the mix the mood you’re trying to set. Is it a bright open image or a dark moody photo? Same lighting with different exposure can be used for both sometimes.
So, how do you meter? A hand held meter with a diffusion bulb on front of the sensor is best. A light meter will read for your exposure as an 18% gray reflective surface, which is pretty close for skin tones. Keeping this in mind, hold the meter pointing toward the camera lens (or where it will be) not toward the light. You want to measure the amount of light that will be bouncing toward the camera, not the amount being generated total. If you are shooting a rim lighting shot, pointing the meter toward the camera will give you a way overexposed reading. The reason being is that you are now metering for the shadow portion of the image instead of the area you want to expose for. In this situation, meter in the direction the subject will be facing.
The idea for metering is to measure the exposure value of the brightest part of the image as the light will be hitting it. Keep this in mind when deciding what you want the exposure to be for. For a high key set up the meter will be for the subject, not the background. For a low key shot, the metering should be for the very small portion that is getting hit by the light. So, for rim lighting (a low key shot) it will be the ridge of the subject. Since the light will be playing across a very small portion of the area visible to the camera, then measure the side that is away form the camera that will be getting the full value and expose for that since the value will be the same for the small part you will be photographing.
If you are shooting a backlit subject for a silhouette, then measure the light directly instead of toward the camera. You will want the subject to go completely black with the exposure being for background giving it the contrast needed. Meter accordingly.
Most meters are designed to measure a strobe exposure at the ideal setting for the camera sync. Dragging the shutter will change the exposure value by allowing more ambient light to enter in. Keep this in mind when setting the camera. You might have to stop the camera down a bit to compensate.
Meters are pretty well calibrated straight from the factory. Still, they should be tested by shooting. Meter the setup, and then bracket the frames without anything moving. Look at the uncorrected images (or negatives) and determine where the exposure should be. If the image exposes better at a different setting than the meter registered, then adjust the meter to read accordingly. If shooting digital, use the histogram to determine the exposure of the scene and if it’s under or over. DO NOT JUDGE IT BY THE SCREEN IMAGE, THEY ARE NOT CALIBRATED. USE THE HISTOGRAM, NUMBERS DON’T LIE!!!
Some Tech Terms
Ambient Light: Light that is naturally available and usually not controllable. The model lights in the strobes is an ambient light source as is window lighting or any other source outside of what is being used for the lighting setup.
Fall Off: Fall off is the decreasing intensity of the light as it moves further away from the subject or beyond the edge that the light has been directed. It is most noticeable at times around the edges of a wider angled shot that shows up as a vignette.
Spill Light: Spill is the light that affects part of the image that you did not want it too. An example would be if you were lighting a subject for a low key or rim lighting, the light that strays onto the background (which you didn’t want to) is the spill off light from your main light source. It is controlled with a honey comb or barn doors.
Dragging the Shutter: Sometimes it is advantageous to make an exposure longer than the recommended flash sync of the camera. The reason for doing this is to allow more ambient light into the exposure. This will give a slight blurring in the studio along with a color shift from the modeling lights. Doing this can cerate a slightly smoother and warmer skin tone. Another reason would be on location in order to bring the background exposure into alignment with the foreground that was hit by the flash.
Sunday, April 11, 2010
getting the exposure right
Getting The Exposure Right
Photography is nothing more than recording light and what it is doing. A painter uses paints to express their vision, and a composer uses music. As a photographer, your medium of expression is light.
Cameras, lenses, filters, lights and various other pieces of equipment are all only tools used to help you achieve your capture of light in the fashion you want to. So to that end, and understanding of how light works and how the different tools can be used to modify it to your vision is essential to the successful completion of your art. The following is an overview of different tools and how to use them.
Lenses and Light
The single most important piece of equipment after the camera itself is the lens. Without a lens, the camera is useless. So what exactly does a lens do? In the most basic terms a lens takes the random light flying around all over the place and directs it onto the film or sensor in a focused manor that can be then recorded. Light bounces off objects as it hits them in a very random fashion, think of a water balloon hitting something and breaking open with water splashing in all directions. That is how light behaves when it strikes an object. A lens will take those multi directional rays and bend them to be of a constant direction in relation to the curvature of the lens. Stacking more lenses in series will modify the direction of the light further and the end result is a sharp in focus image for your camera to record.
Components of a lens
The overall construction of a camera lens is rather basic. It consists of a barrel that is the housing for everything, the lenses, an iris and a mechanism to move the lenses forward and back to achieve focus.
The lenses can be rather simple groupings with as few as two lenses or as many as 15 (the most I’ve personally heard of). The main elements are the front and rear lenses. The front lens has the job of gathering in the light and directing it into the barrel and the other elements inside. The rear lens is the one that takes the light and actually projects it onto the film or sensor plane.
The brightness of a lens is measured in its “f” ratio. The closer the f ratio is to 1, the brighter the lens. The f- ratio of a lens is determined by two factors, those are the focal length (fl) and the diameter (d) of the lens. The f- ratio is figured out with the equation: f l/d=f -ratio. So a lens with a focal length of 50mm and a diameter of 10mm will have a f ratio of f5. The same lens focal length of 50mm but on a lens with a 20mm diameter will have a value of f2.5, So for a lens with a 10mm focal length to have the same f2.5 ratio as the 50mm lens, to only needs to have a diameter of 4mm. Both lenses even though they are different diameters will transmit the same level of brightness through them due to the difference in focal length. This is why different elements within a lens grouping do not have to all be the same diameter to achieve the same f -ratio.
The next piece of the equation is the iris. The iris consists of thin metal pieces that are interlocked to close down or open up to create a variable opening for light to pass through. What this effectively does is change the diameter of the lens in front of it. A lens with a now much smaller diameter with changing its focal length now has a lower f ratio. This is where the f stop numbers come from, the ratio that is now created from the new smaller or larger apparent lens diameter.
Fixed Focal vs Zoom
Long before we had zoom lenses, we were stuck with having to use a wide variety of different fixed focal length lenses. The early zooms were bulky, slow and lacked the sharpness of a fixed. Modern optics and construction materials have greatly lightened the burden of the zoom as well as increasing its ability to deliver a sharp image.
A zoom lens operates by using elements that effectively change the focal length of the lens within the barrel. By moving elements back and forth you are able to change the point where light interacts with certain elements thus shortening or lengthening the focal length of the overall lens (you can not change the focal length of an individual lens without altering it’s shape).
Benefits of a zoom: With a variable focal length you are able to utilize different aspects such as compression and composition without changing or needing multiple other lenses.
Disadvantage: Due to more elements needed, image clarity does suffer to an extent. Zoom lenses are also traditionally slower than their fixed counterparts. High end glass for a zoom does get very pricey.
Benefits of a Fixed: Faster and sharper than their zoom brethren. If you want razor sharp images and shallow DOF, these are the best and usually cheaper than a zoom with the same f ratio.
Disadvantages of a Fixed: You will need to have more lenses to cover the range usually needed for work. The price advantage is quickly eaten up by volume.
Best scenario: Have a good set of zooms that cover the ranges you use most. A 24-70 f2.8 and a 20-200 f2.8 is a great set. If you have a certain focal length you prefer for a higher percentage of images you shoot (say you like a 135mm for portraits) then get a fixed lens with a good speed to it, say f1.8, to use for this work.
The other consideration is the glass itself. Fluoride glass is a low dispersion glass that produces excellent image quality with lighter weight than its regular quartz glass cousins. It is a much higher priced commodity though. The Canon “L” series lenses utilize this glass. As a general rule it is not recommended to use the kit lens. The glass quality is usually low and the f- ratio is normally high.
The lenses you buy will be the one long-term investment in photography. Especially with digital, expect to replace your body every few years as technology makes better and better sensors. The lens will continue to work with new bodies, so a high end lens will still be in use 20 years from now if taken care of even if you’re on your 10th body.
Why use different focal lengths?
So why use a telephoto lens instead of just getting close up on something? With subjects like wild animals or sporting events it is easy to understand why you can’t go up 2 feet away from what you’re shooting to get a shot. But what about models or still life?
There is more to focal length than how close something looks to you. A telephoto lens does not magnify something that is far away to make it bigger; it gives you a smaller angle of coverage as the focal length increases. So using basic geometry you can see that by using a longer lens, you can effectively limit the amount of surrounding items seen in your image.
Another thing to consider when choosing the focal length to use is the compression factor of the lens. Whatever is closest to the lens will appear larger than objects further away. The perceived distortion is in direct relation to the percentage of the distance from the lens. So, using a wide angle lens and getting close up on the subject means that the 1 ft difference between the nose and the back of the head is a much bigger percentage at 3 feet than it is at 20 feet. The distortion will be greater thus making the nose (which is closer to the lens than the back of the head) appear much larger than it really is.
This can be used effectively to show vastness for a landscape, or separate an object from its far distant background. Using a longer lens though can be effective for compressing the distance between foreground and background. Using a longer lens with a more open aperture will also create a much more shallow depth of field effect.
Exposure Value
There is only one correct exposure value for any given image. That is not to say that you can only expose an image one way. Depending on what you want to accomplish there are multiple ways to get to the right exposure. The same subject with identical lighting conditions can even be given a different exposure value for a different look altogether. Both exposure values are correct, but only for each individual look you were trying to achieve.
That is a topic for multiple posts though. In this set of notes I will cover how to change your exposure value using the 3 variables available with a camera and the difference each one will give you for the same exact exposure value (EV).
The definition of Exposure is: The total amount of light allowed to fall onto the photographic medium during the process of taking a photograph.
Please note that there is no exact right amount named in the definition.
The three variables available to you on your camera to control the EV are Shutter Speed, Aperture and ISO. These three are on the points of a triangle that shifts in size, yet must remain equilateral in shape.
For each shift in the direction of favor of one of the variables, the other two must compensate in some fashion.
A smaller aperture for improved depth of field will result in a slower shutter speed thus having a greater possibility of motion blur. To increase the ISO to compensate for the shutter speed can introduce greater noise and less detail.
Here is a chart for one set of exposure values and how they change based off of changing the ISO. This is not a chart for any specific condition, just to show the relationship
F ratio Shutter speed at ISO
100 200 400 800 1600
2.8 4000
4 2000 4000
5.6 1000 2000 4000
8 500 1000 2000 4000
11 250 500 1000 2000 4000
16 125 250 500 1000 2000
22 60 125 250 500 1000
32 30 60 125 250 500
45 15 30 60 125 250
Most digital cameras now a days allow you to adjsut exposure values in third or quarter stop increments with options to fine tune it between those even. The chart is done in traditional 1 stop increments.
So the options give you a trade off of…
Higher shutter speed:
Freezes motion more readily. Great for sports or other action shots such as wildlife. Does require either a wider aperture or higher ISO to achieve so be prepared for their disadvantages.
Slower shutter speed:
Since it requires a smaller aperture, you will have agreater depth of field. This is at the cost of freezing motion. This can be useful with still life or landscapes one windless days. Another feature is that it can add a sense of motion from the blurring that might occur. Very long shutter speeds can be used to blend water together for waterfalls.
Opened up aperture:
Increases the amount of light in allowing for higher shutter speeds to freeze motion. It does come with a shallower DOF however. This can be used effectively to blur out background for portraits (called the bokah of an image). Careful focusing is often required.
Closed down aperture:
Increases your DOF to make focusing less critical. You will decrease your shutter speed to compensate thus loosing the ability to freeze motion or possibly hand hold a lens during the exposure.
Higher ISO value:
This is the “sensitivity” value of your medium to gather light. In film it is accomplished with larger pieces of silver, for digital it is through gain, or amplificaiton of the data collected. Depending on the camera being used, grain or pixilation can start to occur rather quickly as the ISO is upped. This is expecially evvident in shadow and darker color detail. The sensitivity of the digital sensor does not change when you alter the ISO, it only changes how the data is processed. At higher ISO’s the camera will fill in missing information which is what causes the grain.
Photography is nothing more than recording light and what it is doing. A painter uses paints to express their vision, and a composer uses music. As a photographer, your medium of expression is light.
Cameras, lenses, filters, lights and various other pieces of equipment are all only tools used to help you achieve your capture of light in the fashion you want to. So to that end, and understanding of how light works and how the different tools can be used to modify it to your vision is essential to the successful completion of your art. The following is an overview of different tools and how to use them.
Lenses and Light
The single most important piece of equipment after the camera itself is the lens. Without a lens, the camera is useless. So what exactly does a lens do? In the most basic terms a lens takes the random light flying around all over the place and directs it onto the film or sensor in a focused manor that can be then recorded. Light bounces off objects as it hits them in a very random fashion, think of a water balloon hitting something and breaking open with water splashing in all directions. That is how light behaves when it strikes an object. A lens will take those multi directional rays and bend them to be of a constant direction in relation to the curvature of the lens. Stacking more lenses in series will modify the direction of the light further and the end result is a sharp in focus image for your camera to record.
Components of a lens
The overall construction of a camera lens is rather basic. It consists of a barrel that is the housing for everything, the lenses, an iris and a mechanism to move the lenses forward and back to achieve focus.
The lenses can be rather simple groupings with as few as two lenses or as many as 15 (the most I’ve personally heard of). The main elements are the front and rear lenses. The front lens has the job of gathering in the light and directing it into the barrel and the other elements inside. The rear lens is the one that takes the light and actually projects it onto the film or sensor plane.
The brightness of a lens is measured in its “f” ratio. The closer the f ratio is to 1, the brighter the lens. The f- ratio of a lens is determined by two factors, those are the focal length (fl) and the diameter (d) of the lens. The f- ratio is figured out with the equation: f l/d=f -ratio. So a lens with a focal length of 50mm and a diameter of 10mm will have a f ratio of f5. The same lens focal length of 50mm but on a lens with a 20mm diameter will have a value of f2.5, So for a lens with a 10mm focal length to have the same f2.5 ratio as the 50mm lens, to only needs to have a diameter of 4mm. Both lenses even though they are different diameters will transmit the same level of brightness through them due to the difference in focal length. This is why different elements within a lens grouping do not have to all be the same diameter to achieve the same f -ratio.
The next piece of the equation is the iris. The iris consists of thin metal pieces that are interlocked to close down or open up to create a variable opening for light to pass through. What this effectively does is change the diameter of the lens in front of it. A lens with a now much smaller diameter with changing its focal length now has a lower f ratio. This is where the f stop numbers come from, the ratio that is now created from the new smaller or larger apparent lens diameter.
Fixed Focal vs Zoom
Long before we had zoom lenses, we were stuck with having to use a wide variety of different fixed focal length lenses. The early zooms were bulky, slow and lacked the sharpness of a fixed. Modern optics and construction materials have greatly lightened the burden of the zoom as well as increasing its ability to deliver a sharp image.
A zoom lens operates by using elements that effectively change the focal length of the lens within the barrel. By moving elements back and forth you are able to change the point where light interacts with certain elements thus shortening or lengthening the focal length of the overall lens (you can not change the focal length of an individual lens without altering it’s shape).
Benefits of a zoom: With a variable focal length you are able to utilize different aspects such as compression and composition without changing or needing multiple other lenses.
Disadvantage: Due to more elements needed, image clarity does suffer to an extent. Zoom lenses are also traditionally slower than their fixed counterparts. High end glass for a zoom does get very pricey.
Benefits of a Fixed: Faster and sharper than their zoom brethren. If you want razor sharp images and shallow DOF, these are the best and usually cheaper than a zoom with the same f ratio.
Disadvantages of a Fixed: You will need to have more lenses to cover the range usually needed for work. The price advantage is quickly eaten up by volume.
Best scenario: Have a good set of zooms that cover the ranges you use most. A 24-70 f2.8 and a 20-200 f2.8 is a great set. If you have a certain focal length you prefer for a higher percentage of images you shoot (say you like a 135mm for portraits) then get a fixed lens with a good speed to it, say f1.8, to use for this work.
The other consideration is the glass itself. Fluoride glass is a low dispersion glass that produces excellent image quality with lighter weight than its regular quartz glass cousins. It is a much higher priced commodity though. The Canon “L” series lenses utilize this glass. As a general rule it is not recommended to use the kit lens. The glass quality is usually low and the f- ratio is normally high.
The lenses you buy will be the one long-term investment in photography. Especially with digital, expect to replace your body every few years as technology makes better and better sensors. The lens will continue to work with new bodies, so a high end lens will still be in use 20 years from now if taken care of even if you’re on your 10th body.
Why use different focal lengths?
So why use a telephoto lens instead of just getting close up on something? With subjects like wild animals or sporting events it is easy to understand why you can’t go up 2 feet away from what you’re shooting to get a shot. But what about models or still life?
There is more to focal length than how close something looks to you. A telephoto lens does not magnify something that is far away to make it bigger; it gives you a smaller angle of coverage as the focal length increases. So using basic geometry you can see that by using a longer lens, you can effectively limit the amount of surrounding items seen in your image.
Another thing to consider when choosing the focal length to use is the compression factor of the lens. Whatever is closest to the lens will appear larger than objects further away. The perceived distortion is in direct relation to the percentage of the distance from the lens. So, using a wide angle lens and getting close up on the subject means that the 1 ft difference between the nose and the back of the head is a much bigger percentage at 3 feet than it is at 20 feet. The distortion will be greater thus making the nose (which is closer to the lens than the back of the head) appear much larger than it really is.
This can be used effectively to show vastness for a landscape, or separate an object from its far distant background. Using a longer lens though can be effective for compressing the distance between foreground and background. Using a longer lens with a more open aperture will also create a much more shallow depth of field effect.
Exposure Value
There is only one correct exposure value for any given image. That is not to say that you can only expose an image one way. Depending on what you want to accomplish there are multiple ways to get to the right exposure. The same subject with identical lighting conditions can even be given a different exposure value for a different look altogether. Both exposure values are correct, but only for each individual look you were trying to achieve.
That is a topic for multiple posts though. In this set of notes I will cover how to change your exposure value using the 3 variables available with a camera and the difference each one will give you for the same exact exposure value (EV).
The definition of Exposure is: The total amount of light allowed to fall onto the photographic medium during the process of taking a photograph.
Please note that there is no exact right amount named in the definition.
The three variables available to you on your camera to control the EV are Shutter Speed, Aperture and ISO. These three are on the points of a triangle that shifts in size, yet must remain equilateral in shape.
For each shift in the direction of favor of one of the variables, the other two must compensate in some fashion.
A smaller aperture for improved depth of field will result in a slower shutter speed thus having a greater possibility of motion blur. To increase the ISO to compensate for the shutter speed can introduce greater noise and less detail.
Here is a chart for one set of exposure values and how they change based off of changing the ISO. This is not a chart for any specific condition, just to show the relationship
F ratio Shutter speed at ISO
100 200 400 800 1600
2.8 4000
4 2000 4000
5.6 1000 2000 4000
8 500 1000 2000 4000
11 250 500 1000 2000 4000
16 125 250 500 1000 2000
22 60 125 250 500 1000
32 30 60 125 250 500
45 15 30 60 125 250
Most digital cameras now a days allow you to adjsut exposure values in third or quarter stop increments with options to fine tune it between those even. The chart is done in traditional 1 stop increments.
So the options give you a trade off of…
Higher shutter speed:
Freezes motion more readily. Great for sports or other action shots such as wildlife. Does require either a wider aperture or higher ISO to achieve so be prepared for their disadvantages.
Slower shutter speed:
Since it requires a smaller aperture, you will have agreater depth of field. This is at the cost of freezing motion. This can be useful with still life or landscapes one windless days. Another feature is that it can add a sense of motion from the blurring that might occur. Very long shutter speeds can be used to blend water together for waterfalls.
Opened up aperture:
Increases the amount of light in allowing for higher shutter speeds to freeze motion. It does come with a shallower DOF however. This can be used effectively to blur out background for portraits (called the bokah of an image). Careful focusing is often required.
Closed down aperture:
Increases your DOF to make focusing less critical. You will decrease your shutter speed to compensate thus loosing the ability to freeze motion or possibly hand hold a lens during the exposure.
Higher ISO value:
This is the “sensitivity” value of your medium to gather light. In film it is accomplished with larger pieces of silver, for digital it is through gain, or amplificaiton of the data collected. Depending on the camera being used, grain or pixilation can start to occur rather quickly as the ISO is upped. This is expecially evvident in shadow and darker color detail. The sensitivity of the digital sensor does not change when you alter the ISO, it only changes how the data is processed. At higher ISO’s the camera will fill in missing information which is what causes the grain.
Friday, April 2, 2010
Color Management
Color management is the practice of controlling the quality of your images through use of various tools in a multitude of programs. Color management is dealing primarily with the control of color, contrast, saturation, and exposure of the image. Some areas of concern are.
White Balance: Or color temperature. This determines the overall cast of the image. The white balance setting when taking the photo with the camera will determine the processes the camera applies to the original image. If shooting in RAW you will be able to alter it to whatever you would like later. If shooting in jpeg, then you are stuck with the setting.
Contrast: Contrast deals with the range of white to black in the image. Low contrast will have a wide range of tones and sometimes not have a true white or black. High contrast will have an absolute black and white within the image, but very little tonal range in between the two.
Exposure: This is determined by the initial settings on the camera when shooting. It can be adjusted somewhat when shooting in Raw, not in jpeg. The exposure will determine the amount of detail available with the image. An over exposed image will have blown out highlights with no detail and no real chance of bring them back. An under exposed image will have highlight detail, but none in the shadows and will normally have some “noise” associated with the d-min areas. You can add some more density to the shadows, but the detail will no be there.
Saturation: This deals with the intensity of the colors in the image. Zero saturation will be B/W. Be careful with using saturation usage. Over saturating an image will give bad transitions and can create an unrealistic look.
Raw Vs Jpeg
Jpeg is a lossy format for digital imaging. In order to compress the file to save storage space, the algorithm for jpeg takes a sampling of the areas around each pixel and “combines” similar ones together. The lower the quality setting, the more liberal it is with judgment on similarities and will compress the image info more. When you open the image, the algorithm is reversed and detail filled back in. As with any mathematical equation, there will be slight variations every time you open, make changes and resave. Detail can be lost over time when working on images multiple times. This is what makes it a lossy format. When shooting in jpeg, you are already not recording all the information that your camera is capable of obtaining due to the compression of the files generated.
Raw is the native format for digital camera. It is the equivalent to having a digital negative in terms of correction ability. As the name implies, Raw is nothing but the raw data the camera captures for any image regardless of any settings beyond exposure you might have set. An under or over exposed image is still under or over exposed in Raw and will suffer accordingly.
The advantage is that any other processing the camera would have done is still an option in post production. White balance can be completely changed from what was shot, and the image will appear as if it had been shot that way initially.
Raw records the maximum amount of data possible from your camera. It will generate the largest size file also. When shooting, it is best to shoot in Raw and then convert with corrections to a printable format. Printers will not print from a Raw file. Each camera model does have it’s own unique tag on the Raw file that will require either the camera software for conversion or that Photo Shop has the tag for it. When new cameras come out, you will be able to download an update for the tag.
Color Space
sRGB is a color space developed by HP and Microsoft to best simulate the colors available in web based imaging. It is a limited color space that is designed to look good on the lowest common denominator monitors in use. SRGB encompasses about 35% of the visible colors in its range
Adobe 1998 RGB was developed by Adobe to be worked in for the color range that is reproducible in the photographic field. It has 50% of the visible colors available in its gamut, for about a 50% increase in the palate. The colors most affected by the increase are deep greens brighter magentas and oranges (skin tones fall here), and more subtle variations in high tones. Again the Adobe 1998 RGB will capture more data for you when shooting. If you want to discard it later, then you will have the option.
Choosing a color space to shoot in is only a factor when shooting in jpeg. When shooting in Raw the camera will automatically capture the highest amount of information. When converting the files to a printable format is when you will want to decide whether to choose sRGB or Adobe 1998 RGB
8 bit vs. 16 bit
What is a bit
A bit is the amount of information assigned to a pixel in terms of color value. An 8 bit image will have 256 color values assigned to it and a 16 bit image will have 4096 color values assigned to it. This will produce a smother gradation through color blends. Some of these are not even visible to the human eye, and only a very few printers can even process a 16 bit image to output. Not really worth the effort since there is no feasible way to handle the output, and with very rare exceptions will you even be able to tell the difference.
Tools for Dealing with Color Management
For this class we will be dealing with the tools used in Photoshop. These tools are available in all versions of Photoshop.
Levels: (ctrl+L) Levels work with Histograms which are a graph of the exposure values in the image. The right end is the highlights, the left is shadow and there will be a slider in the middle to control midtones. This is a general overall tool. You will be able to bring the highlights slider to the start of detail in the image, bring the shadow slider to the ending of detail and do an overall adjustment to the midtones. It is a limited tool that will not allow you to isolate a specific range in the tones for adjustment.
Curves: (ctrl+M) This is the most useful tool overall. With curves you will be able to isolate a very specific range of tones in the image and adjust them without affecting the rest. You will also be able to make corrections to the individual color channels independently of each other.
Color Balance: (ctrl+B)A good tool for adjusting overall casts, not very useful for dealing with specific colors. The slider bar interface allows you to adjust the entire image, but not isolate a specific range.
Selective Color: Very good tool for correcting a color shift within a specific color group (I.e red, green, blue, etc…) Simply select the color you want to adjust then using the slider bars adjust the cast of it. A good use is when there is an individual with a very red complexion while everyone else is normal. To adjust the complexion, just select the red color to correct in the pull down menu, go to the magenta slider and take some out. Since the person’s skin is red and not the other people, just his complexion will be affected. Be careful though, if someone is wearing a red outfit it will be affected too.
Chanel Mixer: This tool allows you to mix in detail and density from one color channel to another (I.e red into green). This can be useful for dealing with an overall cast, but is a heavy handed tool with no finesse to it. A very little of this tool goes a very long way.
Hue / Saturation: Great tool for what it does. Basically this tool allows you to increase or decrease the intensity of the colors in the image. An image with a very strong cross cast, such as a red highlight and cyan shadows, can be helped by lowering the saturation to even out the tones. You can also increase the saturation to bring out muted colors on an overcast day, or brighten up fall colors and sunsets even more. Be very careful not to over saturate colors. Skin tones can quickly become blotchy and unnatural.
Shadow Highlight: Perhaps one of the most useful tools in the adjustment menu. What this tool does is equalize the exposure values between highlights and shadows. There are slider bars (also use the expanded options window) that let you control the amount of highlight and shadow equalization going on. Take some practice to find good balances, there are no written in stone numbers to enter in since each image will have it’s own set of problems to fix.
Brightness / Contrast: Simply adjust the brightness and or the contrast via two slider bars. Much finer and more precise control using curves.
Desaturate: (Shift+ctrl+U) Averages all the color values of the bit depth of the pixel to create a grey scale image.
Match Color: Used to match colors from one image to another. Be very careful when using this tool. The color to match and the color to match it to must be picked very carefully. Due to shading that occurs on images, just being slightly off on the density of the two spots you are choosing can result in very different overall images.
Replace color: Used to replace one color with another. Again, be very careful with this. The color you are choosing to replace might be slightly present in another area (such as skin tones) that you do not want to alter.
Variations: Can be somewhat useful when first starting off. The variations option will show you the image as it is right now and then create a series of corrected images around it with color and density variations. You choose the one you like best and it then creates a new series of variations based off of that choice. You keep selecting a variation until the one that is the standard in the ring is what you want.
There are other options in the Adjustment menu, most are used for working in layers and will be covered in other classes.
Image Modes
What are image modes
Image modes options are different ways to save or present the information in the image.
Bitmap: Very low rez and incredibly limited colors. Just stay away from unless it is text only.
Greyscale: A B/W image with no color information at all.
Doutone: A two channel image consisting on two separate colors. These can be any two colors you want. Some sepia tone images us this mode with a brown color and a black channel to ad depth to the shadows.
RGB: The preferred mode for photographers This mode has three channels consisting of Red Green and Blue that are mixed together for form all the other colors. This creates the widest range of colors usable by printers, monitors, and visible by the human eye. This is an additive color space that deals with light mixing. In other words, if you ad equal amounts of each color of RGB you will get white. This is how film and photo paper work.
CMYK: The color space used by the printing press industry utilizing inks, or reflective colors that absorb color rather than light that generates it. This is a subtractive space that ads colors to create black.
LAB: A space specifically designed for digital imaging. The three channels deal with light (or luminescence), color and two channels dealing with color casts and contrast.
Indexed Color: A conversion dealing with assigning a profile to the image that will be used for a very specific process later, such as for a printing press with certain characteristics. No need to use with photography.
Multi Channel: CMYK with out a K (black) channel. Produces a very washed out image. The reason for this deals strictly with pre press applications for printing on offset presses. Will never be used in photography except for the incredibly rare times it might be useful in creating masking channels. Not even worth discussion.
Other controls
In programs such as Lightroom, Bridge, and other RAW conversion engines you will have some other non color related options to mull over. Here is a list of some of them and what to do with them.
Contrast: Controls the starkness of the image. Or to phrase it differently, the quickness for pure black to pure white. A low contrast will have a wider gamut of tones and might even be lacking in a true black or white. These images are often called muddy or flat. Contrasty images will be lacking in gradation between density ranges. Blacks will often be blocked up and highlights can quickly become blown out. Find the right level for the image. There is no ideal setting though, each image will vary from lighting situation to lighting situation.
Clarity: Sometimes also called detail. This is a localized contrast variable used to create a stronger differential between densities giving an illusion of finer detail being shown. A little goes a long way with this tool. Setting your Clarity too high will result in jaggy lines around some areas, so keep an eye on it.
Sharpness: This is another contrast differential tool, but on a more global scale than Clarity. Again be very careful with this tool as over usage will quickly result in pixilated detail. Stepping will occur first in finer lined detail such as hair and eyes. There is no way to bring an out of focus image into clear focus. I really don’t care what they show being done on TV shows, it isn’t possible. If detail is not in the original image, there is no way to create what is not there. Sharpness will, however, make an already focused image razor sharp.
White Balance: Or color temperature. This determines the overall cast of the image. The white balance setting when taking the photo with the camera will determine the processes the camera applies to the original image. If shooting in RAW you will be able to alter it to whatever you would like later. If shooting in jpeg, then you are stuck with the setting.
Contrast: Contrast deals with the range of white to black in the image. Low contrast will have a wide range of tones and sometimes not have a true white or black. High contrast will have an absolute black and white within the image, but very little tonal range in between the two.
Exposure: This is determined by the initial settings on the camera when shooting. It can be adjusted somewhat when shooting in Raw, not in jpeg. The exposure will determine the amount of detail available with the image. An over exposed image will have blown out highlights with no detail and no real chance of bring them back. An under exposed image will have highlight detail, but none in the shadows and will normally have some “noise” associated with the d-min areas. You can add some more density to the shadows, but the detail will no be there.
Saturation: This deals with the intensity of the colors in the image. Zero saturation will be B/W. Be careful with using saturation usage. Over saturating an image will give bad transitions and can create an unrealistic look.
Raw Vs Jpeg
Jpeg is a lossy format for digital imaging. In order to compress the file to save storage space, the algorithm for jpeg takes a sampling of the areas around each pixel and “combines” similar ones together. The lower the quality setting, the more liberal it is with judgment on similarities and will compress the image info more. When you open the image, the algorithm is reversed and detail filled back in. As with any mathematical equation, there will be slight variations every time you open, make changes and resave. Detail can be lost over time when working on images multiple times. This is what makes it a lossy format. When shooting in jpeg, you are already not recording all the information that your camera is capable of obtaining due to the compression of the files generated.
Raw is the native format for digital camera. It is the equivalent to having a digital negative in terms of correction ability. As the name implies, Raw is nothing but the raw data the camera captures for any image regardless of any settings beyond exposure you might have set. An under or over exposed image is still under or over exposed in Raw and will suffer accordingly.
The advantage is that any other processing the camera would have done is still an option in post production. White balance can be completely changed from what was shot, and the image will appear as if it had been shot that way initially.
Raw records the maximum amount of data possible from your camera. It will generate the largest size file also. When shooting, it is best to shoot in Raw and then convert with corrections to a printable format. Printers will not print from a Raw file. Each camera model does have it’s own unique tag on the Raw file that will require either the camera software for conversion or that Photo Shop has the tag for it. When new cameras come out, you will be able to download an update for the tag.
Color Space
sRGB is a color space developed by HP and Microsoft to best simulate the colors available in web based imaging. It is a limited color space that is designed to look good on the lowest common denominator monitors in use. SRGB encompasses about 35% of the visible colors in its range
Adobe 1998 RGB was developed by Adobe to be worked in for the color range that is reproducible in the photographic field. It has 50% of the visible colors available in its gamut, for about a 50% increase in the palate. The colors most affected by the increase are deep greens brighter magentas and oranges (skin tones fall here), and more subtle variations in high tones. Again the Adobe 1998 RGB will capture more data for you when shooting. If you want to discard it later, then you will have the option.
Choosing a color space to shoot in is only a factor when shooting in jpeg. When shooting in Raw the camera will automatically capture the highest amount of information. When converting the files to a printable format is when you will want to decide whether to choose sRGB or Adobe 1998 RGB
8 bit vs. 16 bit
What is a bit
A bit is the amount of information assigned to a pixel in terms of color value. An 8 bit image will have 256 color values assigned to it and a 16 bit image will have 4096 color values assigned to it. This will produce a smother gradation through color blends. Some of these are not even visible to the human eye, and only a very few printers can even process a 16 bit image to output. Not really worth the effort since there is no feasible way to handle the output, and with very rare exceptions will you even be able to tell the difference.
Tools for Dealing with Color Management
For this class we will be dealing with the tools used in Photoshop. These tools are available in all versions of Photoshop.
Levels: (ctrl+L) Levels work with Histograms which are a graph of the exposure values in the image. The right end is the highlights, the left is shadow and there will be a slider in the middle to control midtones. This is a general overall tool. You will be able to bring the highlights slider to the start of detail in the image, bring the shadow slider to the ending of detail and do an overall adjustment to the midtones. It is a limited tool that will not allow you to isolate a specific range in the tones for adjustment.
Curves: (ctrl+M) This is the most useful tool overall. With curves you will be able to isolate a very specific range of tones in the image and adjust them without affecting the rest. You will also be able to make corrections to the individual color channels independently of each other.
Color Balance: (ctrl+B)A good tool for adjusting overall casts, not very useful for dealing with specific colors. The slider bar interface allows you to adjust the entire image, but not isolate a specific range.
Selective Color: Very good tool for correcting a color shift within a specific color group (I.e red, green, blue, etc…) Simply select the color you want to adjust then using the slider bars adjust the cast of it. A good use is when there is an individual with a very red complexion while everyone else is normal. To adjust the complexion, just select the red color to correct in the pull down menu, go to the magenta slider and take some out. Since the person’s skin is red and not the other people, just his complexion will be affected. Be careful though, if someone is wearing a red outfit it will be affected too.
Chanel Mixer: This tool allows you to mix in detail and density from one color channel to another (I.e red into green). This can be useful for dealing with an overall cast, but is a heavy handed tool with no finesse to it. A very little of this tool goes a very long way.
Hue / Saturation: Great tool for what it does. Basically this tool allows you to increase or decrease the intensity of the colors in the image. An image with a very strong cross cast, such as a red highlight and cyan shadows, can be helped by lowering the saturation to even out the tones. You can also increase the saturation to bring out muted colors on an overcast day, or brighten up fall colors and sunsets even more. Be very careful not to over saturate colors. Skin tones can quickly become blotchy and unnatural.
Shadow Highlight: Perhaps one of the most useful tools in the adjustment menu. What this tool does is equalize the exposure values between highlights and shadows. There are slider bars (also use the expanded options window) that let you control the amount of highlight and shadow equalization going on. Take some practice to find good balances, there are no written in stone numbers to enter in since each image will have it’s own set of problems to fix.
Brightness / Contrast: Simply adjust the brightness and or the contrast via two slider bars. Much finer and more precise control using curves.
Desaturate: (Shift+ctrl+U) Averages all the color values of the bit depth of the pixel to create a grey scale image.
Match Color: Used to match colors from one image to another. Be very careful when using this tool. The color to match and the color to match it to must be picked very carefully. Due to shading that occurs on images, just being slightly off on the density of the two spots you are choosing can result in very different overall images.
Replace color: Used to replace one color with another. Again, be very careful with this. The color you are choosing to replace might be slightly present in another area (such as skin tones) that you do not want to alter.
Variations: Can be somewhat useful when first starting off. The variations option will show you the image as it is right now and then create a series of corrected images around it with color and density variations. You choose the one you like best and it then creates a new series of variations based off of that choice. You keep selecting a variation until the one that is the standard in the ring is what you want.
There are other options in the Adjustment menu, most are used for working in layers and will be covered in other classes.
Image Modes
What are image modes
Image modes options are different ways to save or present the information in the image.
Bitmap: Very low rez and incredibly limited colors. Just stay away from unless it is text only.
Greyscale: A B/W image with no color information at all.
Doutone: A two channel image consisting on two separate colors. These can be any two colors you want. Some sepia tone images us this mode with a brown color and a black channel to ad depth to the shadows.
RGB: The preferred mode for photographers This mode has three channels consisting of Red Green and Blue that are mixed together for form all the other colors. This creates the widest range of colors usable by printers, monitors, and visible by the human eye. This is an additive color space that deals with light mixing. In other words, if you ad equal amounts of each color of RGB you will get white. This is how film and photo paper work.
CMYK: The color space used by the printing press industry utilizing inks, or reflective colors that absorb color rather than light that generates it. This is a subtractive space that ads colors to create black.
LAB: A space specifically designed for digital imaging. The three channels deal with light (or luminescence), color and two channels dealing with color casts and contrast.
Indexed Color: A conversion dealing with assigning a profile to the image that will be used for a very specific process later, such as for a printing press with certain characteristics. No need to use with photography.
Multi Channel: CMYK with out a K (black) channel. Produces a very washed out image. The reason for this deals strictly with pre press applications for printing on offset presses. Will never be used in photography except for the incredibly rare times it might be useful in creating masking channels. Not even worth discussion.
Other controls
In programs such as Lightroom, Bridge, and other RAW conversion engines you will have some other non color related options to mull over. Here is a list of some of them and what to do with them.
Contrast: Controls the starkness of the image. Or to phrase it differently, the quickness for pure black to pure white. A low contrast will have a wider gamut of tones and might even be lacking in a true black or white. These images are often called muddy or flat. Contrasty images will be lacking in gradation between density ranges. Blacks will often be blocked up and highlights can quickly become blown out. Find the right level for the image. There is no ideal setting though, each image will vary from lighting situation to lighting situation.
Clarity: Sometimes also called detail. This is a localized contrast variable used to create a stronger differential between densities giving an illusion of finer detail being shown. A little goes a long way with this tool. Setting your Clarity too high will result in jaggy lines around some areas, so keep an eye on it.
Sharpness: This is another contrast differential tool, but on a more global scale than Clarity. Again be very careful with this tool as over usage will quickly result in pixilated detail. Stepping will occur first in finer lined detail such as hair and eyes. There is no way to bring an out of focus image into clear focus. I really don’t care what they show being done on TV shows, it isn’t possible. If detail is not in the original image, there is no way to create what is not there. Sharpness will, however, make an already focused image razor sharp.
Sunday, March 28, 2010
digital camera usage 101
Digital Camera Usage
Shooting modes
Auto programs
Full Auto: This allows the camera to select everything for you in terms of exposure. It will decide the aperture and shutter speed along with ISO and white balance.
Sports: This is a shutter priority setting. The camera will choose the highest possible shutter speed and adjust the aperture and ISO accordingly.
Landscape: This is an aperture priority setting. The camera will select the best aperture for the focal length and then adjust the shutter accordingly.
People (or Portrait): The priority is placed on an averaging exposure for a skin tone.
Please note that in all of the program modes, jpeg is the only format available. Auto White Balance is also defaulted to and the camera will set the exposure for an average of the percentages of tones. If you are wanting to shoot a silhouette, high key, low key, or studio lit set up, the camera won’t let you decide that.
Manual and Priority modes
TV (or shutter priority): Select the shutter speed, which will remain locked, and the camera will adjust the aperture as you move around from lighting condition to lighting condition.
AV (or aperture priority): Select your aperture for depth of field and it will remain locked. The camera will now adjust the shutter speed to match the selected aperture.
M (or full manual): You independently set the aperture and shutter speed for your taste. This takes all decision making away from the camera and puts it in your hands. Best for studio lighting since it allows you to adjust your exposure for the look you want. Also, the camera has no way of metering once the shutter has been released, therefore it will be unable to judge exposure values.
ISO Settings
The ISO (or film speed to use an old term), sets the sensitivity of the chip for your exposure. The higher the ISO, the less light needed for an exposure. Also, the higher the ISO, the more grain the image will have. Grain will become more quickly evident with even the slightest under exposure at higher ISO settings.
One advantage digital has over film is the ability to change ISO mid shoot, maybe even for a few frames only, without having to load a roll of film for it or have a separate camera.
Guide for ISO
100: Good for bright sunny days, shooting in the studio with strobes. Highest quality with lowest grain.
200: Good for overcast days, shooting at sunrise or sunset.
400: Ideal for indoor with mounted camera flash. Also good for very overcast days or shooting sports when a very high shutter speed is needed to freeze action.
800: Can also be used for indoor shooting when there is a low level of available light, such as a dance floor. Good for stage lighting also.
1600: use for available light in churches. Or other events that a flash would be inappropriate for, or too distant to be effective. This speed has the highest grain and gain (contrast) of the options.
File Formats
Jpeg vs. Raw
Jpeg is a lossy format for digital imaging. In order to compress the file to save storage space, the algorithm for jpeg takes a sampling of the areas around each pixel and “combines” similar ones together. The lower the quality setting, the more liberal it is with judgment on similarities and will compress the image info more. When you open the image, the algorithm is reversed and detail filled back in. As with any mathematical equation, there will be slight variations every time you open, make changes and resave. Detail can be lost over time when working on images multiple times. This is what makes it a lossy format. When shooting in jpeg, you are already not recording all the information that your camera is capable of obtaining due to the compression of the files generated.
When shooting in jpeg mode, the settings you select for the camera, namely white balance, will be applied permanently. If the white balance is too far off, you will not be able to correct it. Color shifts and cross curves (opposite color casts within the tones of the image) are much harder, if not impossible to correct in a jpeg file.
Raw is the native format for digital camera. It is the equivalent to having a digital negative in terms of correction ability. As the name implies, Raw is nothing but the raw data the camera captures for any image regardless of any settings beyond exposure you might have set. An under or over exposed image is still under or over exposed in Raw and will suffer accordingly.
The advantage is that any other processing the camera would have done is still an option in post production. White balance can be completely changed from what was shot, and the image will appear as if it had been shot that way initially.
Raw records the maximum amount of data possible from your camera. It will generate the largest size file also. When shooting, it is best to shoot in Raw and then convert with corrections to a printable format. Printers will not print from a Raw file. Each camera model does have its own unique tag on the Raw file that will require either the camera software for conversion or that Photo Shop has the tag for it. When new cameras come out, you will be able to download an update for the tag.
But don’t think that Raw is the save all answer. You will still need to get the exposure right. An underexposed image by several stops will still be lacking in the shadow detail the properly exposed image would have held. Same with overexposed, if the highlight detail is gone, it’s gone and pulling the exposure value down in a program will not bring it back. I recommend being no more than ½ stop off plus or minus from ideal for best results.
Color Space
sRGB vs. Adobe 1998 RGB & Adobe Pro
sRGB is a color space developed by HP and Microsoft to best simulate the colors available in web based imaging. It is a limited color space that is designed to look good on the lowest common denominator monitors in use. SRGB encompasses about 35% of the visible colors in its range
Adobe 1998 RGB was developed by Adobe to be worked in for the color range that is reproducible in the photographic field. It has 50% of the visible colors available in its gamut, for about a 50% increase in the palate. The colors most affected by the increase are deep greens brighter magentas and oranges (skin tones fall here), and more subtle variations in high tones. Again the Adobe 1998 RGB will capture more data for you when shooting. If you want to discard it later, then you will have the option.
Adobe Pro is a newer color space designed for an even fuller gamut of color. Designed for the newer monitors it is great for digital designers with better gradations.
Choosing a color space to shoot in is only a factor when shooting in jpeg. When shooting in Raw the camera will automatically capture the highest amount of information. When converting the files to a printable format is when you will want to decide whether to choose sRGB or Adobe 1998 RGB
File numbering and other card care stuff
When using a new CF Card for the first time, select the FORMAT option on the camera and have the camera format the card. This will wipe any thing off the card, and give you the full amount a storage available.
When going to delete images. You can either delete single images, or delete all. When choosing the delete all option, the camera will actually delete the images, not the folders that they are in. Later when you go to download the new images, there will be several empty folders on the card that had never been deleted. To get rid of the images and the folders, choose the FORMAT option on the camera and reformat the card.
Should you reformat or delete images by accident, the images are most likely (not definitely) there. Until you shoot new images and write over the old ones, there is a possibility to recover the deleted images. There are several programs out that specialize in image data recovery from CF Cards. The free one from Lexar (available at their website) is excellent.
When selecting the numbering options on a camera, if you will be shooting more than one card for an event or trip, it is best to select the continuous option. If not selected then the camera will start over at 1 every time you put a new card in. If there will be more than one card used, then you will have several images #1. From an organizational standpoint, this makes life much more difficult for you.
Keep cards while not being used in a carrying case that closes tight. This will keep dust and dirt out of the port contacts and help improve data flow fro the camera to the card, and then from card to camera.
The difference in CF Cards is mainly in the speed of them. The higher the speed, the faster the camera can write to them, and a computer can copy from them. Unless you are a sports photographer, the write speed from camera is not much of an issue. Rarely will you need to fire 10+ shots off in rapid succession in the studio (moving toddlers excepted of course), and then have to wait for the camera to catch up in writing from the buffer. The difference will be in the post production. You will save time in copying the files onto the computer for editing. If you have a big event to download, the time savings could be considerable.
Sensor Maintenance
It is important to keep the camera sensor clean. Dust on the sensor will result in black spots on the images. This is due to the light being blocked by the dust from registering on the sensor. The sensor will see this as a shadow and result in a dark spot.
Take the lens off the camera, select SENSOR CLEAN in the menu and OK it. The mirror will lock in the up position and you can then clean the sensor.
DO NOT TOUCH THE SENSOR WITH ANYTHING NOT SPECIFICALLY DESIGNED TO DO SO WITH!!!!!
The best way to clean is with either a sensor vacuum or swabs designed to be used for the specific purpose of cleaning sensors. Do not blow on the sensor, the moisture from your breath can fog it, and accidental spit will spot it. Both will result in poor image sharpness. Do not use high pressure air, this can damage the sensor. Hold the camera angled down so that dislodged dust will fall out of the camera and with a back and forth motion, gently swipe off the sensor. Turn the camera off to reset the mirror.
Never used compressed air on your sensor. Canned air is made up of gas in a liquid state, you can accidently hit your sensor with some of the liquid and cause serious damage to it.
Delkin makes a great cleaning kit with a sensor vacuum and cleaning wands. It also includes a magnifier with light for inspection of the sensor. Make sure not to touch the bristles on the vacuum, the oil from your fingers will then smear across the sensor.
LCD Screen
The only option you have on the LCD screen adjustment is brightness. This is listed on the menu. You will not have a contrast or color adjustments available. Because of this, you can not adjust the screen on the back of the camera to be 100% accurate to what has been shot. Never judge the quality of the image or exposure value based on the image being shown on the camera back. This will be covered in the Histograms section.
Custom Parameters
There is an option on most cameras to set up custom parameters for different shooting situations. The most common set of variables you can adjust are Contrast, Sharpness, Saturation, and Color Tone. They are used as follows.
Contrast: Your tonal range available between the absolute white and absolute black in the image. The higher the contrast the lower the range of tones available. Images will have harsher transitions. The lower the contrast the more tones between absolute Black and white. Images will be flatter and more muddy with tones running together at lower contrast settings. Depending on the situation will determine the contrast range you want. A very overcast or even foggy day will benefit from a higher contrast, while Very sunny day will need a lower contrast to help even out shadows and highlights in the image.
Sharpness: The sharpness determines the degree of the sharpening filter applied to the image. While it might seem the sharper the image, the better, that’s not always the case. When dealing with small details or contrasting boundaries, images can be over sharpened. The best example would be fine hair catching some backlight against a dark background. The fine detail of the hair when over sharpened will result in stepping of the image area. Stepping occurs when the smooth transition of a line is made to look jagged, like a series of steps. It is most prevalent around areas that are very contrasting in tonal ranges. This includes areas of secular highlights such as catch lights in the eyes, hair and lips. If the image you’re shooting will not have contrasting areas of tone, then sharpening can be used more. It’s best to experiment with the threshold of the camera in use to determine when stepping will occur.
Saturation: Saturation is the intensity of the color in the image. Zero saturation is B/W, super saturation will render images similar to the Andy Warhol style paintings with diminished transitions in tonal value. Bumping the saturation up for outdoor images, especially in the fall, will give you more vibrant colors. Again this is not always a good thing. Makeup on people will become more apparent, red faced individual will become more so, and smoother skin tone transitions will suffer. One trick is to set the saturation lower when dealing with a person who does have a very red complexion who is grouped in with others who don’t. The color of the redder person will come down faster than that of the others, thus helping to minimize the difference.
Color Tone: Color tone deals with skin tones and other colors to a lesser extent. The “+” setting create a cooler skin tone while the “-“ settings are for warmer shin tones. Experiment to your choice. If shooting in Raw, it’s not needed since you will be adjusting the tones in post production.
If you shoot in Raw, all of these options are not needed. You will apply your own preferences for these variables in post processing.
White Balance
After exposure the single most important setting is the White Balance. Light is a continuous spectrum of colors blending together, the part that we can see is called the visible spectrum. Infra Red is below and Ultra Violet is above. So, at the low end of what we can see are the reds, at the high end are the blues, with all the other colors mixed in between. At the center of our perception is white light.
The human brain will smooth over variables in light temperature and adjust our perception of colors to what it believes they should be. Camera sensors don’t do that. They need to be told what the light temperature is in order to apply an equation to the data to correct it to what we would like it to be. This is the White Balance setting.
Incandescent light produces a yellowish light that is at the lower end of the visible spectrum. It is lacking in blue to balance it out. Therefore the camera must add a certain amount of blue into the image to compensate for it. Set the camera on the incandescent setting and you will be able to get well balanced photos indoors using incandescent light source (filament bulbs). Forget to change the settings and go outside or start using a flash and the images will be very blue. This is because the camera is still applying the blue filtration to overcome the lack of blue light, but is now doing so to a full spectrum image that has the light it was previously missing.
Some Common Light Sources and how the Photograph
Incandescent: Yellowish cast. Indoor floor lamps and regular house lights
Fluorescent: Couple of options. Most common has a green tint to it. Used in offices and some stores. Another has an orange cast, usually found in more industrial settings and some stores. There is a full spectrum fluorescent available that does produce white light. That is what we use at the lab.
Mercury Vapor: Very strong orange color. Found mostly in school gymnasiums and warehouses.
Tungsten: Blue light. Used mostly in Theater and other event hall settings that want to use bright or focused lights.
Camera mounted or Studio Strobes: Full spectrum light sources designed to recreate full daylight colors.
Mixed Lighting
The most troublesome lighting condition a photographer can come across is a bad mixed lighting situation. Some can be easy to remedy such as shooting outdoor under a shade tree. The surrounding area will be full spectrum, while the shade under the tree will be blue. Simply using a fill flash on the camera will add the missing colors in the spectrum without eliminating the feel of the lighting situation.
The most difficult (and sometimes uncorrectable) situation deals with interior shoots that have multiple light sources. Churches are notorious for this. Some staging venues, such as the alters at some churches, will use a mixture of lights to achieve an effect they want. Unfortunately these effect might look good to the human eye, but rarely to a camera.. An example would be a sky light (full spectrum) that is only hitting a certain area, the back portion is then lit with a series of tungsten lights with the front being fluorescent. So, the people in the front of the group will have a green tint, the middle will be normal, and the back will be blue.
Using a camera flash will help, assuming that all the light levels are equal. Otherwise, if one is brighter than the other, there will be some fall off in color in order to balance the exposure. If the venue has decided to use gells on the lights for even more color effects, then it’s near impossible to balance all of those out unless you completely overpower them with a strobe unit.
Shooting in RAW will allow you correct for any one specific light source in post production. If there is a mixed temperature problem, it will not fix them separately within the same photo. A solution is to fix each light source, save the individual corrections as a separate file, and then in Photoshop combine the images to make a final with the values balanced out. This is a lesson that will be covered in a future Photoshop posts.
Exposure
The single most important aspect in getting a good image is making sure the exposure is right. Getting the exposure right with a digital camera is much easier than with film. It is true that digital cameras are much more demanding in terms of getting the exposure right than negative film was, but it is about the same as positive film was.
What makes it easier to get the exposure right is not the little preview of the image that is shown right after the picture is taken, but the histogram option on the camera. LCD screens on cameras can be improperly calibrated, and lacking the ability to correct color and contrast, never can be fully correct. Therefore, do not trust them.
The histogram is the tool to use for determining if the exposure is correct.
Histograms
So what exactly is a histogram? It is simply a chart of statistical data charted in terms of percentages along a linear path. They have been in use long before photography was around and can be applied to almost any situation where you would want to see a visual representation of distribution for just about anything.
In photography, a histogram is a graph of the exposure value placements of the image. The horizontal line represents the brightness value of a pixel. The Value 0 being total black, the value 255 being absolute white. The vertical line is the percentage of pixels that have that value. The more pixels with the density value at that point on the graph, the higher the peak.
An ideal histogram will not have a peak that pushes up against either end of the density range. Doing so will represent an area that will not contain any detail, or ever will. So a histogram with a large spike on the highlight end (right) will be overexposed and the image will be blown out. A histogram with a large spike pushing into the shadow end (left) will be under exposed and blocked up.
That said, there is no such thing as a good or bad histogram. Only the correct one for what you are trying to accomplish with the shot.
A low key image will be heavy on the shadow side, but do not let the exposure to go so low that it will block up. Keep the spike from just touching the max density end of the chart.
A high key image will be heavy on the highlight end of the scale. Be careful to keep the spike from flattening out against to right end, otherwise the image will be blown out and not have any detail.
Look at the image, analyze the percentages of density and where they are in relation to the graph. If you have a large percentage of black in the picture (men in tuxedos, black shirts, etc…) then it is perfectly alright for there to be a large spike at the shadow end of the graph. Again, make sure it is not bottoming out and not keeping detail. Also, if there is a large percentage of white, such as a wedding gown worn by a pale woman standing outside on a bright day, then expect a large spike on the right side of the histogram. Just make sure it doesn’t run up against the right end of the scale, thus blowing the image out and losing all detail.
All a histogram can do is tell you where the percentages are in your exposure, not if it is a good exposure. That is completely up to the photographer to decide. Use judgment in the analysis of the image. The histogram is not a light meter, it will show you the dynamics of the exposure and if any of it falls out of the range of the camera to capture.
Shooting modes
Auto programs
Full Auto: This allows the camera to select everything for you in terms of exposure. It will decide the aperture and shutter speed along with ISO and white balance.
Sports: This is a shutter priority setting. The camera will choose the highest possible shutter speed and adjust the aperture and ISO accordingly.
Landscape: This is an aperture priority setting. The camera will select the best aperture for the focal length and then adjust the shutter accordingly.
People (or Portrait): The priority is placed on an averaging exposure for a skin tone.
Please note that in all of the program modes, jpeg is the only format available. Auto White Balance is also defaulted to and the camera will set the exposure for an average of the percentages of tones. If you are wanting to shoot a silhouette, high key, low key, or studio lit set up, the camera won’t let you decide that.
Manual and Priority modes
TV (or shutter priority): Select the shutter speed, which will remain locked, and the camera will adjust the aperture as you move around from lighting condition to lighting condition.
AV (or aperture priority): Select your aperture for depth of field and it will remain locked. The camera will now adjust the shutter speed to match the selected aperture.
M (or full manual): You independently set the aperture and shutter speed for your taste. This takes all decision making away from the camera and puts it in your hands. Best for studio lighting since it allows you to adjust your exposure for the look you want. Also, the camera has no way of metering once the shutter has been released, therefore it will be unable to judge exposure values.
ISO Settings
The ISO (or film speed to use an old term), sets the sensitivity of the chip for your exposure. The higher the ISO, the less light needed for an exposure. Also, the higher the ISO, the more grain the image will have. Grain will become more quickly evident with even the slightest under exposure at higher ISO settings.
One advantage digital has over film is the ability to change ISO mid shoot, maybe even for a few frames only, without having to load a roll of film for it or have a separate camera.
Guide for ISO
100: Good for bright sunny days, shooting in the studio with strobes. Highest quality with lowest grain.
200: Good for overcast days, shooting at sunrise or sunset.
400: Ideal for indoor with mounted camera flash. Also good for very overcast days or shooting sports when a very high shutter speed is needed to freeze action.
800: Can also be used for indoor shooting when there is a low level of available light, such as a dance floor. Good for stage lighting also.
1600: use for available light in churches. Or other events that a flash would be inappropriate for, or too distant to be effective. This speed has the highest grain and gain (contrast) of the options.
File Formats
Jpeg vs. Raw
Jpeg is a lossy format for digital imaging. In order to compress the file to save storage space, the algorithm for jpeg takes a sampling of the areas around each pixel and “combines” similar ones together. The lower the quality setting, the more liberal it is with judgment on similarities and will compress the image info more. When you open the image, the algorithm is reversed and detail filled back in. As with any mathematical equation, there will be slight variations every time you open, make changes and resave. Detail can be lost over time when working on images multiple times. This is what makes it a lossy format. When shooting in jpeg, you are already not recording all the information that your camera is capable of obtaining due to the compression of the files generated.
When shooting in jpeg mode, the settings you select for the camera, namely white balance, will be applied permanently. If the white balance is too far off, you will not be able to correct it. Color shifts and cross curves (opposite color casts within the tones of the image) are much harder, if not impossible to correct in a jpeg file.
Raw is the native format for digital camera. It is the equivalent to having a digital negative in terms of correction ability. As the name implies, Raw is nothing but the raw data the camera captures for any image regardless of any settings beyond exposure you might have set. An under or over exposed image is still under or over exposed in Raw and will suffer accordingly.
The advantage is that any other processing the camera would have done is still an option in post production. White balance can be completely changed from what was shot, and the image will appear as if it had been shot that way initially.
Raw records the maximum amount of data possible from your camera. It will generate the largest size file also. When shooting, it is best to shoot in Raw and then convert with corrections to a printable format. Printers will not print from a Raw file. Each camera model does have its own unique tag on the Raw file that will require either the camera software for conversion or that Photo Shop has the tag for it. When new cameras come out, you will be able to download an update for the tag.
But don’t think that Raw is the save all answer. You will still need to get the exposure right. An underexposed image by several stops will still be lacking in the shadow detail the properly exposed image would have held. Same with overexposed, if the highlight detail is gone, it’s gone and pulling the exposure value down in a program will not bring it back. I recommend being no more than ½ stop off plus or minus from ideal for best results.
Color Space
sRGB vs. Adobe 1998 RGB & Adobe Pro
sRGB is a color space developed by HP and Microsoft to best simulate the colors available in web based imaging. It is a limited color space that is designed to look good on the lowest common denominator monitors in use. SRGB encompasses about 35% of the visible colors in its range
Adobe 1998 RGB was developed by Adobe to be worked in for the color range that is reproducible in the photographic field. It has 50% of the visible colors available in its gamut, for about a 50% increase in the palate. The colors most affected by the increase are deep greens brighter magentas and oranges (skin tones fall here), and more subtle variations in high tones. Again the Adobe 1998 RGB will capture more data for you when shooting. If you want to discard it later, then you will have the option.
Adobe Pro is a newer color space designed for an even fuller gamut of color. Designed for the newer monitors it is great for digital designers with better gradations.
Choosing a color space to shoot in is only a factor when shooting in jpeg. When shooting in Raw the camera will automatically capture the highest amount of information. When converting the files to a printable format is when you will want to decide whether to choose sRGB or Adobe 1998 RGB
File numbering and other card care stuff
When using a new CF Card for the first time, select the FORMAT option on the camera and have the camera format the card. This will wipe any thing off the card, and give you the full amount a storage available.
When going to delete images. You can either delete single images, or delete all. When choosing the delete all option, the camera will actually delete the images, not the folders that they are in. Later when you go to download the new images, there will be several empty folders on the card that had never been deleted. To get rid of the images and the folders, choose the FORMAT option on the camera and reformat the card.
Should you reformat or delete images by accident, the images are most likely (not definitely) there. Until you shoot new images and write over the old ones, there is a possibility to recover the deleted images. There are several programs out that specialize in image data recovery from CF Cards. The free one from Lexar (available at their website) is excellent.
When selecting the numbering options on a camera, if you will be shooting more than one card for an event or trip, it is best to select the continuous option. If not selected then the camera will start over at 1 every time you put a new card in. If there will be more than one card used, then you will have several images #1. From an organizational standpoint, this makes life much more difficult for you.
Keep cards while not being used in a carrying case that closes tight. This will keep dust and dirt out of the port contacts and help improve data flow fro the camera to the card, and then from card to camera.
The difference in CF Cards is mainly in the speed of them. The higher the speed, the faster the camera can write to them, and a computer can copy from them. Unless you are a sports photographer, the write speed from camera is not much of an issue. Rarely will you need to fire 10+ shots off in rapid succession in the studio (moving toddlers excepted of course), and then have to wait for the camera to catch up in writing from the buffer. The difference will be in the post production. You will save time in copying the files onto the computer for editing. If you have a big event to download, the time savings could be considerable.
Sensor Maintenance
It is important to keep the camera sensor clean. Dust on the sensor will result in black spots on the images. This is due to the light being blocked by the dust from registering on the sensor. The sensor will see this as a shadow and result in a dark spot.
Take the lens off the camera, select SENSOR CLEAN in the menu and OK it. The mirror will lock in the up position and you can then clean the sensor.
DO NOT TOUCH THE SENSOR WITH ANYTHING NOT SPECIFICALLY DESIGNED TO DO SO WITH!!!!!
The best way to clean is with either a sensor vacuum or swabs designed to be used for the specific purpose of cleaning sensors. Do not blow on the sensor, the moisture from your breath can fog it, and accidental spit will spot it. Both will result in poor image sharpness. Do not use high pressure air, this can damage the sensor. Hold the camera angled down so that dislodged dust will fall out of the camera and with a back and forth motion, gently swipe off the sensor. Turn the camera off to reset the mirror.
Never used compressed air on your sensor. Canned air is made up of gas in a liquid state, you can accidently hit your sensor with some of the liquid and cause serious damage to it.
Delkin makes a great cleaning kit with a sensor vacuum and cleaning wands. It also includes a magnifier with light for inspection of the sensor. Make sure not to touch the bristles on the vacuum, the oil from your fingers will then smear across the sensor.
LCD Screen
The only option you have on the LCD screen adjustment is brightness. This is listed on the menu. You will not have a contrast or color adjustments available. Because of this, you can not adjust the screen on the back of the camera to be 100% accurate to what has been shot. Never judge the quality of the image or exposure value based on the image being shown on the camera back. This will be covered in the Histograms section.
Custom Parameters
There is an option on most cameras to set up custom parameters for different shooting situations. The most common set of variables you can adjust are Contrast, Sharpness, Saturation, and Color Tone. They are used as follows.
Contrast: Your tonal range available between the absolute white and absolute black in the image. The higher the contrast the lower the range of tones available. Images will have harsher transitions. The lower the contrast the more tones between absolute Black and white. Images will be flatter and more muddy with tones running together at lower contrast settings. Depending on the situation will determine the contrast range you want. A very overcast or even foggy day will benefit from a higher contrast, while Very sunny day will need a lower contrast to help even out shadows and highlights in the image.
Sharpness: The sharpness determines the degree of the sharpening filter applied to the image. While it might seem the sharper the image, the better, that’s not always the case. When dealing with small details or contrasting boundaries, images can be over sharpened. The best example would be fine hair catching some backlight against a dark background. The fine detail of the hair when over sharpened will result in stepping of the image area. Stepping occurs when the smooth transition of a line is made to look jagged, like a series of steps. It is most prevalent around areas that are very contrasting in tonal ranges. This includes areas of secular highlights such as catch lights in the eyes, hair and lips. If the image you’re shooting will not have contrasting areas of tone, then sharpening can be used more. It’s best to experiment with the threshold of the camera in use to determine when stepping will occur.
Saturation: Saturation is the intensity of the color in the image. Zero saturation is B/W, super saturation will render images similar to the Andy Warhol style paintings with diminished transitions in tonal value. Bumping the saturation up for outdoor images, especially in the fall, will give you more vibrant colors. Again this is not always a good thing. Makeup on people will become more apparent, red faced individual will become more so, and smoother skin tone transitions will suffer. One trick is to set the saturation lower when dealing with a person who does have a very red complexion who is grouped in with others who don’t. The color of the redder person will come down faster than that of the others, thus helping to minimize the difference.
Color Tone: Color tone deals with skin tones and other colors to a lesser extent. The “+” setting create a cooler skin tone while the “-“ settings are for warmer shin tones. Experiment to your choice. If shooting in Raw, it’s not needed since you will be adjusting the tones in post production.
If you shoot in Raw, all of these options are not needed. You will apply your own preferences for these variables in post processing.
White Balance
After exposure the single most important setting is the White Balance. Light is a continuous spectrum of colors blending together, the part that we can see is called the visible spectrum. Infra Red is below and Ultra Violet is above. So, at the low end of what we can see are the reds, at the high end are the blues, with all the other colors mixed in between. At the center of our perception is white light.
The human brain will smooth over variables in light temperature and adjust our perception of colors to what it believes they should be. Camera sensors don’t do that. They need to be told what the light temperature is in order to apply an equation to the data to correct it to what we would like it to be. This is the White Balance setting.
Incandescent light produces a yellowish light that is at the lower end of the visible spectrum. It is lacking in blue to balance it out. Therefore the camera must add a certain amount of blue into the image to compensate for it. Set the camera on the incandescent setting and you will be able to get well balanced photos indoors using incandescent light source (filament bulbs). Forget to change the settings and go outside or start using a flash and the images will be very blue. This is because the camera is still applying the blue filtration to overcome the lack of blue light, but is now doing so to a full spectrum image that has the light it was previously missing.
Some Common Light Sources and how the Photograph
Incandescent: Yellowish cast. Indoor floor lamps and regular house lights
Fluorescent: Couple of options. Most common has a green tint to it. Used in offices and some stores. Another has an orange cast, usually found in more industrial settings and some stores. There is a full spectrum fluorescent available that does produce white light. That is what we use at the lab.
Mercury Vapor: Very strong orange color. Found mostly in school gymnasiums and warehouses.
Tungsten: Blue light. Used mostly in Theater and other event hall settings that want to use bright or focused lights.
Camera mounted or Studio Strobes: Full spectrum light sources designed to recreate full daylight colors.
Mixed Lighting
The most troublesome lighting condition a photographer can come across is a bad mixed lighting situation. Some can be easy to remedy such as shooting outdoor under a shade tree. The surrounding area will be full spectrum, while the shade under the tree will be blue. Simply using a fill flash on the camera will add the missing colors in the spectrum without eliminating the feel of the lighting situation.
The most difficult (and sometimes uncorrectable) situation deals with interior shoots that have multiple light sources. Churches are notorious for this. Some staging venues, such as the alters at some churches, will use a mixture of lights to achieve an effect they want. Unfortunately these effect might look good to the human eye, but rarely to a camera.. An example would be a sky light (full spectrum) that is only hitting a certain area, the back portion is then lit with a series of tungsten lights with the front being fluorescent. So, the people in the front of the group will have a green tint, the middle will be normal, and the back will be blue.
Using a camera flash will help, assuming that all the light levels are equal. Otherwise, if one is brighter than the other, there will be some fall off in color in order to balance the exposure. If the venue has decided to use gells on the lights for even more color effects, then it’s near impossible to balance all of those out unless you completely overpower them with a strobe unit.
Shooting in RAW will allow you correct for any one specific light source in post production. If there is a mixed temperature problem, it will not fix them separately within the same photo. A solution is to fix each light source, save the individual corrections as a separate file, and then in Photoshop combine the images to make a final with the values balanced out. This is a lesson that will be covered in a future Photoshop posts.
Exposure
The single most important aspect in getting a good image is making sure the exposure is right. Getting the exposure right with a digital camera is much easier than with film. It is true that digital cameras are much more demanding in terms of getting the exposure right than negative film was, but it is about the same as positive film was.
What makes it easier to get the exposure right is not the little preview of the image that is shown right after the picture is taken, but the histogram option on the camera. LCD screens on cameras can be improperly calibrated, and lacking the ability to correct color and contrast, never can be fully correct. Therefore, do not trust them.
The histogram is the tool to use for determining if the exposure is correct.
Histograms
So what exactly is a histogram? It is simply a chart of statistical data charted in terms of percentages along a linear path. They have been in use long before photography was around and can be applied to almost any situation where you would want to see a visual representation of distribution for just about anything.
In photography, a histogram is a graph of the exposure value placements of the image. The horizontal line represents the brightness value of a pixel. The Value 0 being total black, the value 255 being absolute white. The vertical line is the percentage of pixels that have that value. The more pixels with the density value at that point on the graph, the higher the peak.
An ideal histogram will not have a peak that pushes up against either end of the density range. Doing so will represent an area that will not contain any detail, or ever will. So a histogram with a large spike on the highlight end (right) will be overexposed and the image will be blown out. A histogram with a large spike pushing into the shadow end (left) will be under exposed and blocked up.
That said, there is no such thing as a good or bad histogram. Only the correct one for what you are trying to accomplish with the shot.
A low key image will be heavy on the shadow side, but do not let the exposure to go so low that it will block up. Keep the spike from just touching the max density end of the chart.
A high key image will be heavy on the highlight end of the scale. Be careful to keep the spike from flattening out against to right end, otherwise the image will be blown out and not have any detail.
Look at the image, analyze the percentages of density and where they are in relation to the graph. If you have a large percentage of black in the picture (men in tuxedos, black shirts, etc…) then it is perfectly alright for there to be a large spike at the shadow end of the graph. Again, make sure it is not bottoming out and not keeping detail. Also, if there is a large percentage of white, such as a wedding gown worn by a pale woman standing outside on a bright day, then expect a large spike on the right side of the histogram. Just make sure it doesn’t run up against the right end of the scale, thus blowing the image out and losing all detail.
All a histogram can do is tell you where the percentages are in your exposure, not if it is a good exposure. That is completely up to the photographer to decide. Use judgment in the analysis of the image. The histogram is not a light meter, it will show you the dynamics of the exposure and if any of it falls out of the range of the camera to capture.
Thursday, March 25, 2010
welcome
Welcome to our new blog from Dowtown Photo. Our goal is to present ideas, techniques and information about photography to help further the understanding of and appreciation for the art of photography. All in a fun format packed with great information. We are looking forward to working with all of you to help you find the tools needed to express your artistic vision through photography.
Tips and tricks from basic through advanced will be shared, becasue what is the point of knowledge unless it is given freely. And while we realize that not all the topics covered will be in areas of specific interests to everyone, we will always try to include something that can be applied to your personal goals as a photographer.
If there are any questions you would like answered, feel free to ask either on this site or our FB fan page and we'll do our best to get answers for you. Some answers might take longer if there is research involved. Where upon we do have quite a bit of information here combined with decades of experience, some of the more obscure info might call for us to check with some specialists we know.
In the future we will be keeping you all updated with leasons ranging from getting the most out of your camera, lighitng in the stuio, posing people, getting that great nature shot, composing your image for the most impact, program and product reviews, post processing your images for the best result, editing in photoshop to create some incredible images, printing out your files (we do prefer doing that here for you) and even getting into videos of how we do it here.
we might even get into Photo Challenges. We'll put out some ideas and see what all of you can come up with.
When you have a question about photography, we want you to think of us first. We're you pro lab photo experts here to help you become the photographer you want to be.
Tips and tricks from basic through advanced will be shared, becasue what is the point of knowledge unless it is given freely. And while we realize that not all the topics covered will be in areas of specific interests to everyone, we will always try to include something that can be applied to your personal goals as a photographer.
If there are any questions you would like answered, feel free to ask either on this site or our FB fan page and we'll do our best to get answers for you. Some answers might take longer if there is research involved. Where upon we do have quite a bit of information here combined with decades of experience, some of the more obscure info might call for us to check with some specialists we know.
In the future we will be keeping you all updated with leasons ranging from getting the most out of your camera, lighitng in the stuio, posing people, getting that great nature shot, composing your image for the most impact, program and product reviews, post processing your images for the best result, editing in photoshop to create some incredible images, printing out your files (we do prefer doing that here for you) and even getting into videos of how we do it here.
we might even get into Photo Challenges. We'll put out some ideas and see what all of you can come up with.
When you have a question about photography, we want you to think of us first. We're you pro lab photo experts here to help you become the photographer you want to be.
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