Fie on Photoshop: Krita, the Real Photoshop Killer - page 2
Krita supports more color spaces than any other FOSS application, which is good news for folks who want to go beyond good old RGB and CMYK. The various color spaces define different gamuts and different colors, so conversion from one to another usually means a loss of color fidelity. Some folks make themselves crazy trying to find a way to define colors precisely and objectively. But this is an impossible task because everyone perceives colors a little differently. 9-12% of men have a degree of red-green blindness, 1-2% cannot distinguish blue from yellow, and approximately 1% of women have some form of color-blindness. It's a master stroke of perversity that makes red and green so important in our culture, and a testament to inertia and indifference that they remain so.
But I digress. When you're editing your images you're either going for technical accuracy, or an emotional fidelity. That's where understanding the pros and cons of the different color spaces helps you to create your best and most pleasing images. While it's good to understand the different color spaces, the three you're most likely to use are RGB, CMYK, and L*a*b*.
The L in L*a*b* (also called LAB and CIELAB) stands for luminosity, and a and b are for the color-opponent dimensions. Using LAB calls for a fair bit of study. It encompasses a very wide color gamut, and you can apply sharpening, contrast, and color corrections that go far beyond what you can do with RGB and CMYK, because it separates color from detail. The a and b channels only define color. The L channel defines luminance, black-white, and brightness. The reigning guru of using LAB to repair and retouch digital images is Dan Margulis. This article, Color, Contrast, and L*A*B*, is an excellent introduction to what LAB is all about. Mr. Margulis is a Photoshop expert, but the same LAB principles apply to all image editors.