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.
Sunday, April 11, 2010
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.
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