I use Adobe Acrobat to change colors in a PDF. Why does mrserge 'convert everything to CMYK' by using the 'Map, spot, process colors' Fixup? Dietrich von Seggern never does. He merely continues in RGB:

Your issue has to do with the color space. The box in question uses ICCbased RGB - but you are right: just decalibrating it does not suffice.

What you should do is first analyze the box in Preflight. You can do so using the "List page objects grouped by type of object" profile and you can limit that to one page.

The screenshot shows that the color of the box is 0.82/0.81/0.88 in RGB. You can now put that value into the Map colors fixup which needs to be set up for the accurate color space of the object.

  • Different methods exists because there are so many different things designers and print workers wants to do with their files. You'll never find an answer to "which tool to use in all cases". Graphic design is a big jigsaw puzzle. You'll never see the full picture, but the more pieces you learn about the easier it gets. Do you know about print production and inks? – Wolff Aug 19 '19 at 15:54
  • I would love to take that bounty, but the more I look at this question, the more confused I get. I can't see that @mrserge ever mentions a fixup called "Map, spot, process colors". Am I overlooking something? If you mean "Why convert to CMYK first if you can just map directly from the spot color to CMYK white?", then I think you are right. But mrserge might have chosen this way because it was easier to explain. Anyway, if it works for you to omit that step, I guess you can just omit it. – Wolff Nov 21 '19 at 21:03
  • @Wolff Sorry; my typo. See the screenshot under step 5; mrserge chose 'Map colors'. – NNOX Apps Nov 22 '19 at 3:24
  • @Wolff 'If you mean "Why convert to CMYK first if you can just map directly from the spot color to CMYK white?' I think I was asking a different question. I rewrote my post: clear now? – NNOX Apps Nov 22 '19 at 3:24
  • So another way to phrase your question could be "What is the difference between CMYK and RGB"? – Wolff Nov 22 '19 at 16:00

If you're just trying to select all the RGB boxes in your document, it does not matter how you convert the colors to CMYK, as long as you verify what the CMYK values are and enter them into your preflight AFTER the conversion takes place.

However, your suspicion that this isn't necessary is valid. The statement that you can have the preflight profile look at RGB values instead of CMYK is correct.

In the future, if you're going to reference a previous question, in your new question - please actually include the context from the original question and not just a link.


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