I'm working on a photobook project with Blurb. The project contains various enlarged photos (double-page, around A3, horizontal) each one with a subtle gradient on a large area.
I work in 16-bit RGB to avoid banding when grading etc. Once finished I convert to 8-bit RGB, and after that I convert to CMYK via Blurb profile. This gives me also the advantage of the dither option.
The problem is that after this conversion, I like to make a sort of “secondary” grading with Curves properly in CMYK, and at this point I see that 8-bits are few because the gradients start banding.
I could convert from 16-bit RGB to 16-bit CMYK, in order to avoid banding during the “secondary” grading, but in this way I loose the usefull dither option (in fact if I convert 16-RGB to 16-CMYK the dither option is disabled).
So my question: which is the best method to convert from RGB to CMYK remaining at 16-bit, and then changing to 8-bit at the very end WITH dither option?
I don't know if it's correct, but what I'd do is the following: 1st grading in 16-bit RGB, then converting to Blurb's CMYK always at 16-bit, then 2nd grading, then returning to RGB without conversion (simply Mode > RGB), and finally converting again to CMYK 8-bit with dither option.
Does it make sense? Or is there an easier and more elegant method to do the same?
The LSB dither is very subtle. Sometimes stronger noise is needed, still subtle though. You usually don't wan't to introduce noise into the extreme shadows/highlights though. I created an action to avoid that: