Fix colors after or before rgb to cmyk conversion
When I convert from
CMYK in Photoshop as you know colors change saturation and maybe some hue.
So basically what the title asks, does it matter when I adjust the colors and saturation via hue/saturation layer? Or can I fix the colors in
RGB or in
CMYK and it doesn't matter?
Actually, to do things correctly you need to color adjust at least twice.
If you are working in RGB, you should color correct in RGB.
And if you then convert to CMYK, you should color correct again for CMYK.
One color correction is never a good idea if you change color modes.
What I found reading a great book by Dan Margulis "Professional Photoshop: Color Correction, Retouching, and Image Manipulation With Adobe Photoshop" is to work in Lab. When I was working for newspaper and we had a custom made profile RGBtoCMYK so we worked only in RGB. BUT we printed on only one machine that has been profiled to our needs. So we had a profile that converted our corrected RGB to CMYK in a way that gave the best results.
When I tried to apply same workflow in my freelance job I failed miserably (correcting in RGB then changing to FOGRA 29 for example). Sometimes the RIP omitted profiles, sometimes it applied it's own. Sometimes the printhouse had it own profile so my CMYK was far away from result (machine added 10% Magenta while I had none).
So after reading Margulis book I started working with photos in Lab. And it worked great. And by great I mean that even serious mistakes didn't have much influence on photos in the end.