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Tuesday, June 19, 2007

Mysteries Of (Color) Space

We've covered it before and we'll cover it again because the ins and outs of color management begin with a firm grasp of how devices handle color space

Relative Colorimetric

We see the effects of relative colorimetric rendering. The out-of-gamut colors get clipped (Point A) while the colors contained in the smaller gamut remain unchanged (Point B). This ensures that what we see as a white point from the source is remapped as a white point on our output. Typical uses for this rendering are printing, CMYK conversions and, sometimes, press simulation.

Absolute Colorimetric

Absolute colorimetric is used mainly for proof simulation when wanting an RGB device to match that of a CMYK device. With absolute colorimetric, the white points will change to account for the base-paper white of the simulated stock. In other words, if the paper on which the RGB device is printing is fairly bright, there's no way the print will match that of a printing press' yellowish, dingy paper. I realize that “yellowish” and “dingy” are harsh descriptors, but, let's face it, it's terrible stock in comparison. In any event, the RGB device will lay down some extra ink to simulate the proofing stock. Hence, your highlights may look yellowish and dingy.


As the name implies, this intent will saturate the colors for visual appeal. This is used for graphic slides and overhead projectors for presentations.

Between the perceptual and relative colorimetric rendering intents, relative colorimetric seems to be doing the job, for the most part. Perceptual rendering is selected most often when there are a lot of colors that are out of gamut and need to be brought in as much as possible.

Your homework assignment is to acquire an image, employ the color-managed workflow and bring in one image two different ways—one using sRGB and the other using Adobe RGB. Output the images to your printer and convert using both relative colorimetric and perceptual renderings. Try the same method on a subject of very muted colors and another subject of very saturated colors. See any difference?

What, Me, Worry?

Being a professional photographer today requires that you have at least a working knowledge of color space issues and, therefore, an understanding of how to deliver the best image to your client. While we endorse the notion of complete color management from beginning to end in your workflow, the fact remains that once the image leaves your workspace, that's the end of your control, and the image will be at the mercy of the color management of your client. The best you can do is hope that they have been as diligent as you have.




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