The other day, I was helping a person figure out a weird problem in Shake. Given it took two of us to figure out what turned out to be a color space problem, I figured it would worth spending some time discussing color management and Aperture.

Color management is important because, as you may know, no device, screen or printer, can reproduce every possible color, and each device reproduces a different set of colors. The set of available colors for a given device is called a color space. A color profile is just some math that specifies how to interpret pixel values in terms of a particular color space so that when we talk about a specific color, we're clearly and consistently defining the color. If each device we're working with has the proper color profile available (and our tools are setup to use them), then we can say our workflow is calibrated because as we move from file on disk to screen to other screen to printer, the colors stay consistent.

The first profile that matters is the profile in our image file. This profile tells Aperture (or another application, like Photoshop) how the colors in your file are defined. Some profiles, like Adobe 98, specify a large number of possible colors, while other profiles, like sRGB look pretty good even if you're not looking at that file on a properly calibrated monitor. In fact, typically, higher-end cameras create image files using Adobe 98 whereas consumer cameras (where the images often are displayed on uncalibrated monitors) use sRGB.

Once the file and its color information are read in, a color management engine (such as ColorSync) moves the pixels in the file into a flexible working color space, which in tools like Aperture and Photoshop is where we can make adjustments. Adobe Camera RAW for example uses ProPhoto internally as its working space (I believe). To the best of my knowledge, there is no way to specify Aperture's working space. The main reason this matters is that different adjustments can cause different results in different color spaces. Certain colors in your image might not exist in smaller gamut color spaces, for example. Another example of why your adjustments will differ is that some spaces are perceptually linear while others are energy linear. Say you double the exposure in your image. In a perceptually linear space, that means that your image will now appear twice as bright. In an energy linear space, you image might not be twice as bright, even though you've doubled the amount of energy in the pixels. Perhaps an option to set the working space will be available in the future, but I'm guessing there are bigger fish to fry first.

The next profile to deal with, which is one you can control, isn't actually in Aperture: it's under System Preferences > Displays > Color. Here is where you set the system-wide profile that controls how a given color from an application is transformed when it's sent to the screen so that it gets displayed as the expected color. Usually, you use a device like a Spyder 3 to measure your monitor, creating this color profile for your specific display. Just be warned that since your perception varies some under different lighting conditions, it's a good idea to calibrate your monitor in a lighting condition you can recreate, such as a dark room. Make sure to watch your monitor's brightness setting, too and to not change it after calibrating!

Back in Aperture, one great and overlooked color-related feature is Onscreen Proofing. As I mentioned earlier, not every device displays color the same way, and if you're adjusting your image for a specific target (e.g. to make a print), it's nice to be able to see how your image will look when transformed to the printer's color space and printed without wasting any paper. Under View > Proofing Profile, you are able to pick what output profile you want to use (e.g. your printer and paper combination), and then select View > Onscreen Proofing to see how your image will look when transformed to that color space. Sometimes, if the devices reproduce colors similarly, it's tough to see if this command is actually doing anything. To clearly see that yes, something is happening, pick one of the default black & white or sepia profiles.

Lastly, under your image presets, you're able to specify what color profile will be embedded into your exported images. I find that this is incredibly useful for my web and email presets. I've set both to always convert my exported image to sRGB so that even if the person looking at my image has never calibrated his monitor, it will still look reasonable. Another example of when this is really handy is if you're sending your images off to be printed elsewhere, even at Costco! Most labs provide color profiles for their printers online for free. If you make a new preset (i.e. one called "Costco") and set it to use the lab's profile, then Aperture will convert your file to the printer's colorspace. Then, when having your image file printed, make sure to select "no color adjustment," and your print will look like how you expect it to look.

Hopefully this brief overview has cleared up any misunderstandings about color management in Aperture that you might have had! If you're really curious, google around for discussions about Adobe 98 vs. ProPhoto vs. sRGB color spaces, and see how they compare to different monitor and printer spaces.