Neutral Gray

... depends on your color space

The Question: Need an 18% Gray: I am rather new the digital printing and working with Photoshop. I would like some information about getting a particular color (or shade) in Photoshop. What numbers do I have to input to achieve 18% gray (same as Kodak's Gray Card)? I would appreciate any help on this matter. Thanks!

Our reply to a question sent in by: Mike
 

Mike, I wish you would have given a bit more information, like what you want to do with the 18% gray. Grayscale and color "Gray" cards are produced with a very exacting color ink. The ink is formulated to yield a certain color "temperature" when light is reflected off of it. How you plan to use this color in Photoshop is of paramount importance in setting such a value.
      For instance, in RGB mode, equal amounts of RGB will yield a neutral gray. Your #2 step on the step wedge should come in at around 214 for each of the RGB. This is theory however, not science because so many other variables will affect the 'actual' resulting color. Even your monitor will have an effect.
      On the other hand, CMYK has no real solution for an 18% gray other than setting a solid black to 18%. Ideally, the #2 step in CMYK will be C: 25, M: 16, Y:16, and K: 0. This recipe should build the gray from the process colors. However it is not what Kodak considers its 18% gray.
      If you plan to print the project using the gray, then the printer and its inks will have a direct impact on the resulting color. Color matching is a very exacting science and usually doesn't include a computer in the equation -- other than trial and error.
      You can pick up a gray step wedge at most photo supply stores. These can be scanned along with your color material and then used to calibrate the color, and remove color casts. This is actually the most reliable way to adjust scans because you know that the grays are supposed to be balanced values of RGB.
      I hope I've helped you answer your question. If I knew more about your project, perhaps I could zero in more accurately on the solution.
 

From Photoshop 911 Case #0211-02

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