Correct In CMYK Or RGB?
We've been asked the question of whether to correct in CMYK or RGB a hundred times. As a general rule, we try to do as much color correction as possible in RGB mode, and if we're going to use the image on press, we only convert to CMYK at the end of the correction process. The main reason is that CMYK mode throws away dataâ”a lot of dataâ”and why would you want to correct an image with significantly less data than your scanner can capture? We want as much data as possible while correcting images, and when we're done, then we'll convert to CMYK (under Image, choose Mode) and toss the data that won't be used on press.
Pretty short post on a potentially lengthy topic. I wrote a training doc that described all the ins and outs of color correction. It included information about 16bit vs 8bit editing, CMYK vs RGB and a lot more. You are right that upon conversion to CMYK you are losing data. This is because CMYK has a much smaller color gamut than RGB. Another thing to keep in mind is that every edit you make to a file in Photoshop is destructive and degrades the image. Adjustment layers help but not a whole lot. If you can scan your source or export your RAW camera file as a 16bit AdobeRGB file then you will have tons more data to work with. Then when you finish editing you can export your file as an 8bit CMYK for press. And don’t forget to do your color profile conversion correctly. But that’s a whole other post. 😉
One other thing I forgot to mention. You need to set your proof/working color space in Photoshop to whatever your CMYK output is. Otherwise you are correcting for something you can’t see and choosing colors you could never output. Again, this all goes much deeper than simply saying to edit in RGB.