Thom's Quick & Dirty Guide to Color Management


99% of what you need to know in 1% of the space.

Original: 1/14/2008

  • You must manage color. While standards exist for color information, there are quite a few different ones, and they're implemented haphazardly across products. Even Macintosh users, who have color management built into their OS in a more regular way than Windows users, need to manage their color.
  • Profiles are not Spaces. Most of the confusion about color management comes in the terminology, and the biggest confusion point is the difference between a Color Profile (sometimes called a Device Profile) and a Color Space. Note that I use these two terms separately, but the International Color Consortium (ICC) does not. The reason why I separate them is because they are used differently:
    • A Color Space defines what is possible. Imagine you're designing an office building. The bigger the building you design, the more workers it can hold. Color Spaces are the same. The "bigger" the Color Space, the more color definitions it encompasses. Larger Color Spaces not only include more possible colors, but also tend to allow for brighter, more saturated colors, as well. Note that a specific pixel value--say 48,122,240--produces a different color in sRGB than it does in AdobeRGB because of the difference in size of the Color Space; that's why an image shot in one Color Space but displayed or printed in another will look wrong. In order of increasing size, the primary Color Spaces photographers use are sRGB (small space), AdobeRGB (medium space), and ProPhotoRGB (large space).
    • A Color Profile specifies how a device deviates from a Color Space. When we profile a monitor, printer, or sometimes a camera, we are essentially creating a map of how it differs from a Color Space definition. Savvy software can then use that map to "fix" the color when rendered on or by that device so that it matches the Color Space definitions.
    • ICC files are confusing. Color Spaces and Color Profiles are both stored in .ICC files, and the ICC uses the word "profile" to describe both! Technically, that's correct. Practically, that gets you into trouble if you don't pay attention to what's in that file and its purpose. That means you have to know whether the .ICC file you're picking is really the right type for what you're using it for. You don't want to pick Color Spaces to fix device deviancies from the color standards, nor do you want to pick Color Profiles to assign a Color Space to use for color definitions. The most typical problem that occurs along these lines is picking your monitor Color Profile as your Color Space. Remember, in Thom's world, a Profile is not a Space.
  • Your computer software makes it harder than it should be. With the exception of a few recent products, such as Lightroom, you need to be proactive in dealing with color management. That involves:
    • What's your OS do? Windows and Macintosh users Think Different.
      • In OS-X on a Macintosh, color management is always present (Color tab on Displays in System Preferences). Apple provides a basic Profile (Color LCD on my MacBook Pro) that is set by default, but you should select the monitor profile you create (see below; most profilers automatically do this for you by placing their profile into this field). The Macintosh also defaults to a gamma of 1.8 (you should probably profile to 2.2; see gamma, below). But the good news is that OS-X applications are "color aware," meaning that they display colors using whatever Color Profile that's in effect in Displays. Thus, all applications get the device deviance for the monitor automatically adjusted.
      • In Windows XP or Vista, color management generally requires that you create a profile from an external device (I've seen a few monitors and video cards come with Color Profiles, though, so you should check to see if you've got one). Gamma is assumed to be 2.2, which is what you want. But not all applications are "color aware," so you may have to set things like your monitor Color Profile in your software application. This is a real problem, as there is considerable variability on this point and considerable differences in the terms software programs use (see next).
      • Watch out for Adobe Gamma. If this helper application is loaded at startup by your operating system, it's going to try to apply a profile of its own. This can lead to classic "double profiling," which you don't want to do. If you profile with a hardware device as I suggest, make sure Adobe Gamma is disabled.
    • What's your application do? Basically, your application falls into one of two categories: (1) it doesn't need any help with color and you usually have to configure nothing (e.g. Lightroom); or (2) it needs information from you about what to do:
      • Set a Color Space. Photoshop users need to select Color Settings from the Edit menu and set their "RGB Working Space" to the Color Space they wish to use (more on which one in a bit). Capture NX users need to select Color Management from the Preferences menu and set their Default Color Space and their default Printer Profile (used for Soft Proofing). This latter usually entails picking the profile your printer maker supplied for the paper you use.
      • Watch for Color Space mismatches. If you camera is set to sRGB and your application to AdobeRGB, you should see a dialog pop up when you try to open an image if everything is set right. This dialog allows you to accept the camera's definition, assign the application's definition, or convert the data. Generally, you want to avoid conversion upwards in Color Space sizes (e.g. sRGB to AdobeRGB).
  • Any monitor profiler is better than no profiler, and probably good enough. Monitor profilers run from under a US$100 to many times that. The simplest one is probably the Pantone Huey, while the next step up is probably the Colorvision Spyder 3. But you can get monitors with built-in profilers and even more expensive profiles or calibrators if you start looking closely. Does it matter which you buy? Not really:
    • The differences between profilers is small. If you're into absolute precision with color, perhaps because you shoot clothing for fashion catalogs, then maybe you have motivation to look for the very best and most accurate profiler. But for the vast majority of photographers, any decent profiler is a huge step forward in color management. With many of the profilers targeted at photographers, there are software upgrades that make a bit of difference. For example, the difference between the Huey and Huey Pro is software--the Pro version does a more detailed profile with more discrete measurement points. The high-end Spyder software asks you to pre-balance the red, green, blue, and brightness on your monitor using a special pre-profile procedure, which helps it get the best possible results out of your monitor. But the differences you'll see in the high-end versions of these products versus the low-end are very small versus the difference you'll see between profiling and not profiling.
    • The biggest issue is getting the profiler parameters right. Even the profile software sometimes gets in the way. Many throw some cryptic terms and options at you: gamma, white point, and so on. Start with gamma of 2.2 and a white point of D65 (unless you know for sure that your monitor is set to something else; some monitors use the term "color temperature 6500K" instead of "D65"). Later, when you get more color savvy, you can experiment with other options.
    • Don't let your monitor's controls get in the way. Did you tweak the brightness and contrast (and other settings) directly on your monitor? If so, you might need to reset those things. It's best to start from the defaults and only apply settings directly on the monitor that the profile hardware/software suggest.
  • Gamma is not a relative on your mother's side. Gamma refers to how dark to bright is linearized (or not linearized). Cameras see with a gamma of 1.0 (linear). Humans see with a gamma that's not perfectly captured by a number, but gammas in the range of 1.8 to 2.2 generally come close.
    • But set 2.2. The reason for this is all those PCs surfing the Web with an assumed gamma of 2.2. If you profile to the Mac 1.8 gamma standard, those PC users are going to see what looks to be somewhat bright images with an improper shadow linearization.
    • Some software, including Nikon DSLR camera settings, now refers to a gamma adjustment as "brightness." I suspect this is so that you don't confuse "monitor gamma" with "image gamma." But now you'll confuse "monitor brightness" with "image brightness."
  • Printer profiling is a different, more complex story. You're in a twisty maze of printer settings. You're in a maze of twisty printer settings. When it comes time to print, things get very confusing if you're trying to do it yourself (it's not much less confusing if you use a lab, but at least using a lab is very simple by comparison):
    • Who's doing the color management? It's a fight between the application (e.g. Photoshop) and the printer driver (e.g. Epson 2400 driver). They can't both do it, so you have to pick one or the other. I'll give you a simple starting point: use your printer manufacturer's paper and let the printer driver do it and select the manufacturer's paper Device Profiles when you start out. As you get more sophisticated, switch to letting Photoshop do it and use custom paper Device Profiles.
    • Use the right Color Space. Most of the recent desktop inkjet printers come close to the size of the AdobeRGB Color Space. Thus, if you work in sRGB you're losing some of the subtlety you could obtain. Most photo labs have printers that work closer to sRGB (and expect that as the Color Space), so you'd be sending them the wrong data if you used AdobeRGB.
    • Profile your lab. If you have prints regularly done by someone else, check Dry Creek to see if there's a profile available for that lab.
    • Learn Soft Proofing. Most programs that you'd use to print from have soft proofing ability, which is a way of letting you see on screen what the likely output from your printer will look like. Why should there be a difference? Because some printers can't print certain colors, some papers add an underlying color, and so on.
  • What the heck is a Color Mode? Fortunately, Nikon has finally stepped away from that terminology. Basically, Color Modes 1 and 3 were pretty large deviations from "neutral" color, as if you had adjusted Hue, Saturation, or other color modification controls on the camera.
    • I've always suggested Color Mode II. It's the most "neutral" of the Color Modes. My mantra is that "it is always easier to create deviations from normal color than it is to create normal color from deviated colors."
    • The latest cameras don't have Modes. The Picture Control settings now do the color distortions, should you want them.

Thom's Quick Recommendations (all your really need to know):

  1. Set ProPhotoRGB in your converter as your Color Space if you shoot raw (it doesn't matter what the camera setting is). You'll be surprised to know that your DSLR can do much more subtle and extended color than AdobeRGB can do. Fortunately, whatever setting you have in your raw converter will override your camera setting.
  2. Set sRGB as your Color Space if you shoot JPEG and print at labs or if you only output to the Web. Setting anything else means you have to convert your Color Space before sending the image to print or putting it on the Web.
  3. Profile your monitor. This is the best thing you can do to help you achieve good color. And these days, it doesn't cost much. But make sure the monitor profile is only used for the monitor! It's not a Color Space.
  4. Use the printer driver and custom profiles for the paper you print on. All printer makers have profiles for their papers, and most paper manufacturers have profiles now, as well. Only when you know how to print this way should you try anything more sophisticated or switch to having the application handle the color management during printing.
 

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