Relationship between onscreen/printed CMYK and RGB

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“…

Answer

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.

Attribution
Source : Link , Question Author : Skippy le Grand Gourou , Answer Author : Rafael

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