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Fie on Photoshop: Image Editing in Linux - page 2

Overpriced Photoshop Begone

  • January 24, 2008
  • By Carla Schroder
So what are these RGB, CMYK and Pantone thingies? RGB is red, green, and blue. CMYK = cyan, magenta, yellow, and black. Pantone means the Pantone Color Matching System.

RGB is the basis for all colors emitted by computer monitors. We were taught in grade school that all the colors of the visible spectrum can be created by combining red, green, and blue light, even white light, though computer monitors only display a limited gamut. (Gamut is a term you'll see a lot; it means range of colors.) If you were a confused kid like me, you tried to make white by combining red, green, and blue paints. But this never worked, because pigments don't work the same way as light.

So for printing inks CMYK works best, and is the color system used by virtually all commercial printers, and better-quality home inkjet printers. You've seen the blah muddy colors output by low-end RGB inkjet printers, and the murky blacks that aren't really black, but more like the muck that results from grade school kids trying to make white with colored paints. CMYK produces nice crisp true blacks and true colors.

The Pantone Color Matching System goes beyond the CMYK gamut and defines thousands of additional colors, including special colors like flourescent and metallic colors. Colors that are not duplicated in the CMYK gamut are called spot colors. The Pantone company sells printed guides with swatches of each color and their index numbers, like PMS 100. So designers and printers and everyone involved have a common, standard system for specifying what colors to use. Even a lot of supposed professionals don't understand the differences between RGB and CMYK, and think that using a RGB-to-CMYK converter is sufficient. Unfortunately it's not, not even Photoshop's converter; you don't get perfect fidelity, but suffer noticeable color shifts.

Adding Pantone support to Gimp would open a legal morass. It's not entirely clear what Pantone, Inc. "owns". They don't own colors, and they don't own numbers. Copying and re-distributing their color swatch books is an obvious no-no, but what about building some sort of Pantone reference guide into Gimp? Adobe pays licensing fees to Pantone so they can build in a Pantone color-picker.

But the lack of a built-in Pantone color picker isn't such a big deal. Computer monitors vary in color, brightness, and contrast representation, so getting the best fidelity still comes down to matching swatches in a Pantone book. A bigger problem is Gimp not supporting CMYK natively, or higher bit depths. Someday it will--the problem is the core graphics engine is inadequate. It limits Gimp to 8-bit RGB. Modern graphics editors that are not hobbled by legacy code support 16- and 32-bit CMYK. Patience, Gimp fans, the day will come. Meanwhile, what's a Linux user to do?

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