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I'm using InDesign and I am exporting a photo book for an online printing service (Blurb) in PDF/X-3 (I use unaltered an Export profile that they provided). In the Output tab of the Export Adobe PDF Settings, Color Conversion is set to No Color Conversion and Output Intent Profile Name is set to their provided CMYK.

If I'm not mistaken, this means that the photos embedded in the PDF will not be converted to CMYK, but instead will retain their original color space (sRGB/adobeRGB).

What is causing me concern, is that the Ink Limit in the Separation Preview Panel, indicates that the dark areas of these RGB Photos, exceed the desired TAC level by the printer (<300%) (I get red regions up to Ink limit of 340%).

  • Should I do something about it, or is the ink limit of the RGB photos to be managed by the printer and I should not worry?

  • My idea is that I don't need to, since these files will be color managed by the printer on-the-fly - Is there some fallacy in this?

  • How does InDesign decide the ink limit of an RGB image? What CMYK conversion does it apply for these calculations?

  • Well that would be "No Color Conversion" – joojaa Feb 3 '17 at 8:09
  • so @joojaa, would I be correct in assuming that managing the coverage of the RGB photos inside my CMYK document are not my responsibility to be adjusted? – FotisK Feb 3 '17 at 13:32
  • Not sure it is valid pdf-X under this circumstance. In anycase the problem with not doing it yourself is your settin yourself open for mistakes. Color conversion is not a one to one conversion but one to many, your setting yourself up to gods of color conversion and they might catch your intent or not... but you just gave away the only way for you to complain about the result. Naively it works, there are some printhouses that i would trust to do this, some not so much. – joojaa Feb 3 '17 at 14:41
  • Thank you @joojaa, your point about trusting the printhouse is very valid. I've read mixed reviews about Blurb. But since it's mostly catering to people who know nothing about CMYK I assume they have a workflow tuned for RGB. I'm printing a family album and don't mind loosing control over the rendering of the images – FotisK Feb 3 '17 at 15:00
  • regarding the pdf-x settings, they are selected by the Blurb's indesign plug-in and the user is not allowed to change anything. Would you say that these PDF settings don't necessarily retain the colorspaces of the photos? – FotisK Feb 3 '17 at 15:00
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The long and short of it is; ask your printer. Every printer will have a different ink limit and process for dealing with anything over that. Some will send you the file back to correct, some will convert themselves, some will explain this to you, some won't. It should be as easy as asking your printer for a color profile and converting to that profile.

As for the separation preview in InDesign, the ink limit is set by you — there's an input right there for you. The CMYK values it uses are its conversion either to your document profile, working space, or — if you have proof colors enabled — your proof color profile.

A quick example...

This is an RGB JPG placed in InDesign, viewing separations with my working CMYK profile and the ink limit set to 260:

enter image description here

This is the same image with "Proof Colors" enabled and my proof colors set to use a profile that limits ink coverage to 260:

enter image description here

The areas that were over the limit are now limited to 260 (so no red warning areas), since it's using the correct profile. Of course this is just a preview so you need to make sure you correctly assign the profile on output and convert your colors using that profile.

  • Thank you @Cal! Regarding the preview, this is exactly the way I worked. Up to 330% I'd get red areas, and from 350% onwards there was none - hence the ~340% TAC/coverage I mention. – FotisK Feb 3 '17 at 13:37
  • Regarding asking the printer, I have already done that and am awaiting a response, but in this case Blurb tech support answers don't feel definitive (trustworthy). The reason I'm posting here, is because I feel this is a printer-independent issue: My rationale is that since I'm not color managing the sRGB/adobeRGB images (by embedding their individual color profiles inside the PDF/X3 file), and the printer is obviously capable of handling sRGB/adobeRGB images embedded in the PDF, doesn't this also mean that the TAC of these images is not my concern? – FotisK Feb 3 '17 at 13:42
  • (If I was converting the images to CMYK myself, I would probably have to correct the TAC, but I'm not) – FotisK Feb 3 '17 at 13:43
  • Honestly, it depends on the printer. They're certainly capable of managing it themselves, and some will be fine with that but some will insist you send files that are ready. But as I said it should be as easy as asking them for the correct profile and converting to that profile on output. – Cai Feb 3 '17 at 13:47
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    Oh right, yeh if you're advised to send sRGB images then don't worry about the values in InDesign! It's still a good idea to preview how your images will look with the correct proof profile if you can but don't worry about the coverage – Cai Feb 3 '17 at 14:11

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