🚀 go-pugleaf

Tech Illustrator....Conversion to CMYK can be a complicated subject, especially for the uninitiated.

First, whenever a conversion takes place, there is ALWAYS a source profile and a destination profile. If the original file arrives "untagged" with a profile, the one is "assumed" in Photoshop (or InDesign). It's like assuming someone is speaking French, Italian, or Spanish...you need a reference point. You can look at the color settings in these programs to see what the default setting is for both RGB and CMYK. If your defaults are Adobe RGB and US Web Coated SWOP v2, the your untagged RGB file will be assigned Adobe RGB for the purposes of conversion. If this is a correct guess, then you are half way there. If it is an incorrect guess, your color will be off. These days, sRGB or Adobe RGB are the most likely guesses, since they are the most widely used. When you bring your files into PS, try assigning sRGB, Adobe RGB, Apple RGB and ColorMatch RGB, and tag each image with the one that looks best to you. Images can have different RGB profiles, and depending on the source, that is very possible. As long as they all end up with the same (correct) flavor of CMYK, you should be okay, but they need to look correct in RGB before conversion.

The destination profile (press CMYK) is another matter. It would be best if the printer can give you a profile to use. Just saying "give me CMYK files" is a bit like talking and not know what language is being spoken. If they do not have a custom profile, then ask for an "industry standard" profile to use as a target, such as US Web Coated SWOPv2, ISOCoated, etc. If you are printing onto coated stock, you want a coated profile. If you are printing onto UNcoated stock, you want an uncoated profile. If printing in the US on coated stock, US Web Coated SWOP v2 will get you in the ballpark, but it depends on how close the press approximates that standard. In Europe, ISO Coated or Euroscale Coated are decent bets. In Asia, I really don't know.

If you use the "Mode" command to convert to CMYK, it will be converted to the CMYK profile that is set as the default in Color Settings. It is more flexible to use "Convert to Profile", then you can select the profile and rendering intent you want. Sorry, this stuff gets complicated, especially at first.

Depending on the line screen (ie, dots per inch) the printer is using, you may need different resolution files. Assuming high quality files, and a line screen between 133 and 175, you probably want to deliver 300 PPI (pixel per inch) files, which is the normally requested resolution most of the time.

I'd do the conversions to CMYK in Photoshop, then place those converted files into Indesign. There is a lot to know and a number of places you can trip up, so this is a cursory overview.

I'd start by getting some guidance from your printer, the specs they use, or whatever. They may or may not have any. If not, then ask if they try to adhere to North American, European, or Japan standards. This may be a helpful clue. The more info you can get the better.

If they don't give you anything, then you may want to run a short press test first (before doing an entire book run) by converting a few images to different profiles. See which gives you the best results and then use that.

We've only just touched the surface of this complex subject. If you are overwhelmed, see if you can work with a prepress service.

Lou