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Converting RGB to CMYK for photo book

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I am a photographer and am publishing a book of my work. It will be printed at an offset printer overseas (not Blurb, etc). I'm self-publishing so am bearing the full expense. 

I need to convert my RGB image files to CMYK. I've spoken will a color separator who offered great advice, but too expensive to have him do it for me. I am not an expert in color management. The printer will give me an icc file.

So.....is there a video or web site that might offer newbie tips and tricks that I can lean on? Doing a straight conversion in Affinity seems to get things close but I could really use a "top ten things to look for" to help gain confidence in doing this right. What I've found so far seems rather vague. Any photographers been through this before and want to suggest lessons learned?



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Hi darinb,

This is post is a great read: https://affinityspotlight.com/article/designing-for-professional-printing/ 

Ideally you really need the ICC profile from the printer to get the best match and then export the book as a PDF which also uses the same profile.

If the above link doesn't help, let us know which app you are using and we help further :) 

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Hi @darinb,

I work in magazine publishing where we do that RGB to CMYK conversion all the time. From what I read in your post, you want your photos on paper to appear as close as possible to your originals on screen. Whether this can be done to your satisfaction depends on a number of factors, one of them being the colors used in your photos. In addition to what @stokerg suggested, you may want to consider the following:

  • CMYK color spaces are smaller than RGB color spaces. This means that some RGB colors cannot be accurately represented in CMYK. Blue and bright green colors with high saturation will cause trouble.
  • This is a technical limitation that you cannot circumvent. It also means that it's not really prossible to automate the conversion process, at least if you have many different images. You'll want to carefully compare the color appearance for each image and tweak it as needed. Take a break after long sessions and also check your work again the next day.
  • The conversion process itself will only give you limited control over the resulting colors, but you can experiment with different soft proofing settings in Affinity Photo or further edit your CMYK images after the conversion to get closer to the look you want.
  • Provided that color management is set up correctly, computer monitors are capable of accurately rendering the colors as they will appear in your print product. However, the actual look and feel of your photos on paper will still be different because paper is not screen. Carefully select a suitable paper grade and, by all means, make a prepress proof. Instead of just soft-proofing the pages, you'll want to do actual ink-on-paper-proofing.

Kind regards

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Hi @stokerg. Thanks for the link to that page. Useful stuff. I *will* be getting an icc profile for them to match the paper etc.

@kaffeeundsalz Thank you for your thoughts. Very valuable. 

So my basic plan is to make them look good in RGB, convert to CMYK, then tweak it in CMYK to see if I can improve things? I feel so way out of my element when I start reading about ink loads and so forth. Maybe I'm more worried than I should be? Maybe I'm overthinking it?

A few questions: I have a book designer and I will give him to CMYK images which he will then use to replace the low res ones we used to design the book. How important is it that I give him exact-sized images, vs just giving him all images at maximum size and let InDesign do the size adjustment?

Aside from, color, what about sharpening? Sharpen until it looks right on screen, even if not at final size?

We will get two rounds of paper proofs as part of the process, so we will have a chance to make course corrections.

I'm sure one I get this underway it will be more starightforward than it now seems. :)



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I'm by no means an expert, but have some experience printing on a digital press.

My advice would be:

1: Calibrate your monitor. There's no point doing anything else until you are sure your screen is as accurate as it can be.

2: Get the printer icc profile and use it as a soft proof. Adjust your colours etc working against this. Can stay with rgb files, no need to convert colour space at this stage. Don't worry about ink loading etc, that's for the printer to handle and the icc should do all you need on your end.

3: Turn off soft proof, export to pdf with the printer icc profile.

I'd probably resize the images prior to export (obviously keep the original size as well). That way you can control the output rather than hoping the next person down the line makes a good adjustment.

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