Help! All My Images Are The Wrong Color!
Digital imaging can sometimes get more than a bit complicated, especially for the inexperienced. A problem I get asked about from time to time is the understandable frustration of having all your images cursed with a strong color cast. While there may be any number of possibilities, a clue to the most frequent cause can be found in what color the cast itself is.
Blue and orange color casts are familiar even to film shooters as being symptoms of white balance issues. While our eyes automatically adjust to the changing color of light from the warm hues of sunrise through the cooler tones of mid-day back to the warmth of sunset, cameras both film and digital do not. Sure, makers of digital camera try to correct for white balance by averaging out the colors in a scene on the assumption that things overall should be neutral, but this doesn't always work as well in practice as it might in theory. Sometimes we have to help things along a bit. Whatever color the light itself has that is shining on a scene, you need to add the opposite in order to compensate.
Cameras generally have a range of preset white balance choices going by names such as "Cloudy," "Direct Sunlight," and "Shade." If you shoot raw though, your best bet is to basically ignore white balance in camera and to adjust it after the fact during raw conversion. This will let you vary the color temperature from full on ugly blue to devastating orange as well as the spectrum of more natural white balances in between these two ends. If you aren't shooting raw, or have images that have already been converted, you can still fix things to a reasonable degree with the Warming and Cooling Photo Filters in Photoshop and the like. But while adjusting white balance in your raw converter will not affect image quality, doing so after the fact can degrade things to a degree. As such, it becomes more important to get it right in camera for jpeg shooters than for folks who shoot raw.
If all your images have a green or magenta cast, the problem most likely lies not with your camera or with the images that come from it, but rather with the color management settings you have chosen on your computer. This can be both good news and bad since, while it may be comforting to learn that your images are actually fine and that all that is wrong is the way you are choosing to view them, having to dig into color management settings to correct things can intimidate all but the most knowledgeable. It's not that color management is actually difficult, it's just that forces seem to conspire to make it seem that way.
Between the various choices in your operating system (Windows or Mac OS X) together with those in Photoshop and other imaging programs and the ones in your printer driver, there are way too many places where you can enter the name of a color profile. Color management as a whole hasn't been around all that long (it is Adobe RGB 1998 after all) and companies are still working on how best to integrate things into their programs in a user friendly way. And every software manufacturer wants to get in on the act too, so while they continue to duke it out, we're left with way more choices than we actually need. What you need is one way to correct the color being displayed on your monitor, not three. Your printer needs a color profile to compensate for whatever quirks it may have with regard to accurately rendering color, but if you correct for it twice or three times by filling in every possible blank with the correct profile, you will be overcompensating and making things worse, not better. And if having all those places where you can enter a profile name makes it so you really can't figure out which goes where, there's little chance of getting things set up in a way that will work. If you put your mind to it, you can in fact interject the correct printer profile at least four times over on the way from Photoshop to the printed page. You aren't likely to think the end result looks very good of course, but you can do it, either on purpose or more than likely on accident. Yes, there is more than one "correct" way to do things in the world of color management as there is in most aspects of digital imaging, but there are far more ways to set things up incorrectly.
Which leads me to the problems of green and magenta color casts. Profiles for Epson printers (and models from some other manufacturers as well) require profiles that essentially add a degree of magenta to the raw data being sent to the printer driver. These profiles do a great deal more of course, but the obvious effect is to make things more magenta or red. If you apply them more than once, things will go from being what they are supposed to be to becoming over-magenta when you print an image.
Rather than applying it more than once when printing, assigning your printer profile to an image in Photoshop will cause it to look green rather than magenta. This effect is somewhat akin to how you need to add the opposite of the ambient light's prevailing color when correcting white balance. If your printer needs a bit of magenta to make prints come out correct, telling Photoshop that the colors in your image are also a bit too magenta will make it compensate by swinging things back towards the green — the opposite of magenta on the color wheel. Even though you may print on an Epson printer, you shouldn't apply (or convert) that profile to your documents. The document color space is completely independent of the color space for both your printer and your monitor. It is intended simply to let you save your image in a standard color space that can be shared with others regardless of what computer they may have, and to let you continue to use it regardless of what you may get in the future.
But that's not the only way to get a green cast. Turning color management off in Photoshop can do it too. If you do this, images that are correctly saved in sRGB, Adobe RGB or similar "standard" document color spaces will be displayed without appropriate correction. This can cause all sorts of color problems, but green is the most common. While the CMYK color management policy setting can generally be turned off since most of us don't work in CMYK, the RGB policy should be set to either "Preserve Embedded Profiles" or "Convert to Working RGB" depending on your work habits.
Not having a profiled monitor can cause all sorts of color cast problems. If you've ever gone to a big store that has a whole wall of color TVs for sale that are all displaying slightly different colors for the same channel, you know what having a slight misadjustment can do for what you see on a monitor. The fact is, there's really no way for you to know what your images actually look like unless you start with profiling your monitor. Yes, I've written about this before, but it bears repeating as it's amazing how many photographers will spend a couple hundred dollars or more on a new lens but are unwilling to spring half that to get their monitor to display accurate color.
There's no way I can clear up every different cause for color casts in digital imaging, but hopefully this will give you some place to start if you are having color problems.