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I edited a picture book using scribus, color management enabled, with CMYK TIFF images and corresponding profile as input. In principle my screen has been calibrated, though more than one year ago.

I set the output :

  • to PDFX-1a, for "printing", with a CMYK print profile ;
  • to PDF-1.5, for "web", with a "compatible with Adobe RGB (1998)" profile.

Then I sent the first version to a professional printer.

I always assumed the following relationship between versions, expecting onscreen CMYK to be off :

printed CMYK ≃ onscreen RGB ≠ onscreen CMYK

And indeed when color management is enabled in scribus the rendering of CMYK pictures is that of RGB.

However I just received the printer's proofs, and the actual relationship is as follows :

printed CMYK = onscreen CMYK ≠ onscreen RGB

Did I miss something, or is my workflow presumably wrong ?

Update :

My understanding of the CMYK workflow was indubitably wrong, but I was strongly mislead by the "compatible with Adobe RGB (1998)" profile(which is scribus' default). I figured using the sRGB profile for screen rendering gives colors much more similar to the CMYK rendering. It seems a known fact : quoting WP entry on Adobe RGB color space, "all of the adjustments made CMYK conversion worse than before"…

  • Could also be your printer. Depending on the method they are using to print, it could cause colors to shift and the fact they match your onscreen CMYK is just a coincidence. – iAmBentley Nov 8 '16 at 19:37
  • If this were true what would be the point of onscreen cmyk? – joojaa Nov 8 '16 at 20:32
  • @joojaa See comment below Rafael's answer (written while you wrote yours). I have yet to understand how conversion between both color spaces are that different. I mean, if the screen is able to simulate CMYK rendering, how comes the CMYK->RGB conversion gives different colors ? – Skippy le Grand Gourou Nov 8 '16 at 20:41
  • @SkippyleGrandGourou It can't it can only simulate the colors that are within gamut. Or alternatively shrink colors so they are relatively to each other same in the new fitted gamut. Depending on how it did the conversion there may not be going back (see there are 4 ways to do it, especially perceptual and saturation intent are poison), also the conversion is not unique it could be done in many ways so round tripping might be problematic. CMYK mostly, but not entirely, fits neatly within RGB but not the other way around. See this 3d graph – joojaa Nov 8 '16 at 20:57
  • @joojaa Yes, I think I understand that. What I don't get is why a particular color, e.g. cyan-like in CMYK on screen (and on print, actually), gets blue-ish in RGB. It's clearly not a matter of being able to display it since it is already. But maybe I just have to read more on perceptual mode et al. – Skippy le Grand Gourou Nov 8 '16 at 21:14
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printed CMYK = onscreen CMYK ≠ onscreen RGB

This is correct

Viewing a cmyk on a calibrated image, with the correct software simulates on screen how the print will be.

You will not have bright happy greens, etc.

printed CMYK = onscreen RGB

This has not much sense, because on a simple RGB file you have not told the computer what needs to be simulated, so thoose greens and happy colors are just sitting there to be viewed as such.

There are a lot of variables while converting a file to CMYK: Color profiles, overprint, rich black.

Some programs do treat RGB asuming they all at the end will be converted to CMYK if you turn the simulation on by default on them. But others not, because you could need an online publication for example.

  • Damn, I always thought "working in CMYK" was only about conversion for printing, not a color space one would litterally work with... (Actually, bright happy greens are my very concern, but on the CMYK version...) – Skippy le Grand Gourou Nov 8 '16 at 20:34

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