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I have a book ready for printing. But, of course, it was done in RGB. In fact, I stretched the RGB gamut beyond its normal range in order to make it more painterly etc.

When I saw it converted to CMYK, I almost passed out. All the great colors I had achieved in RGB had been dulled and "grayed". It was a great disappointment even after infinite tweaking of the CMYK colors in a futile attempt to get them back to match the original RGB colors. Worst of all was the color blue. No matter what I did in CMYK to restore this very important color, all I got was a gray-blue.

Is it possible in this remarkable age of technology that there is no printing press that can print a book directly from RGB?

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  • There is a particular blue pigment used in 19th century landscape paintings that used to come out as violet on kodak 5x7 positive film transparencies. I know your pain.
    – horatio
    Apr 4, 2014 at 19:57
  • See also Simplest set of inks that could print the RGB gamut? - but the short answer here is, either pay a bit extra for a blue spot colour or two, or use 'nearly blues' like C100,M60,Y0,K0, get real proofs (it usually looks better when printed, the greyness is exagerated a touch on screen to show the contrast with spot colours), and talk to the printer if you're not satisfied
    – user56reinstatemonica8
    Apr 11, 2014 at 13:27

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RGB is a color space that can only exist with projected light. It's physically impossible to replicate it on paper, which is a reflected light color space.

So no, no printing press can 'print RGB'.

At best, prepress RIP software can convert from RGB to CMYK. In fact, this is what most prepress software workflows do.

How they convert to CMYK can vary wildly, of course, so you may very well have better results with one method over another.

Ideally, your printer would provide you with color profiles that you would use in your software to best match their workflow. If you don't have these, ask them if they can provide them to you.

Ultimately, though, you simply can't replicate your RGB colors fully in CMYK.

If you have the money/willingness, there are things you can do to enhance CMYK, however. This would include:

  • investing in brighter/coated paper (the brighter the paper, and the smoother the surface, the more light will reflect)
  • considering using more than 4 colors. (Hexachrome printing was one such model that used 6 color printing. Some inkjet printers now do the same)
  • Add spot colors. A spot color is a custom ink that can be mixed beyond the color space CMYK can provide. For instance you can use metallic ink, or dayglo, or varnish, etc or--in your case--a custom blue ink.
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    I was typing an answer, but this covers it. I will say from, personal experience, that you will always have better results doing your own CMYK conversions than leaving the conversion to the printer's proof/plate stage.
    – horatio
    Apr 4, 2014 at 19:52
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RGB color is for light-producing situations, and is additive, which means that you are adding light of one color to light of another color, resulting in more light and a mixed color.

CMYK color is for light-absorbing situations, and is subtractive, which means that you are absorbing light instead of reflecting it, and mixing two pigments results in different but not more light being reflected.

The two spaces do not overlap completely, and cannot.

If you are desperate for a wider gamut in your printed materials, and have the budget, consider printing processes with more than four pigments. Many consumer inkjet printers use CcMmYK, including light cyan and light magenta, while Pantone has a patented system that adds orange and green inks. Both of these would produce better blue colors than a simple CMKY printer.

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