Are you ready for a long read? 🙂 Here’s an article that seems to have a few insights into some of the intricacies of CMYK in InDesign <-> Photoshop. https://creativepro.com/my-cmyk-images-change-when-i-print-or-export-pdf/
So I should ask him if the the printer we’re using is offset and if it is I should use “press quality” with colors converted to CMYK?
Yes, do ask him whether it’s an offset machine or not. (I think both offset and “digital” printers use CMYK, while inkjet printers like my Canon Pro-100 do not.) It would be good to clarify what we’re working with here, but he’s almost surely working with something that needs CMYK input, since he mentioned “toner”.
Here’s an article that gives the basics of RGB vs. CMYK.
But what is the option mean to “preserve numbers”?
If I’m reading that article correctly, it means that InDesign should not “re-convert” any files that are already in the CMYK color space. (CMYK colors are interpreted by computers as a series of numbers). i.e. yes, you do want to preserve numbers.
Here’s what I would suggest.
- Start back from LR with your edited RAW files.
- Do your edits, sharpenings, etc in PS, but DON’T set a CMYK profile in Photoshop.
- Import the RGB files to ID, (you can actually import PSD files if you choose)
- And when you’re all done, export to PDF and only then tell ID to do the CMYK conversion at that point.
- After you’ve received another proof, go back and edit as needed for brightness, exposure, etc… following the exact same workflow. (RGB -> InDesign -> export a CYMK .pdf file)
Of course all your careful work could be lost if your printer does any sort of conversion or “saving” so make sure to ask him what you need to do so that he doesn’t have to change anything.
I will admit that I’m quite a novice in this whole printing business myself, so if @jamesstaddon has better advice, I hope he shows up to give it. 🙂 I recently was responsible for typesetting/layout of a ~150 page book with about 40 pages of photos in it, so I’ve been working through some of this stuff myself. It’s quite a headache, and even professionals sometimes strongly disagree on what’s the “best” way to do things. (As you will see if you read the comment section below that first article I linked to.)