Separation curves and the histogram
2001-08-14 by Todd Flashner
I'm like the atheist who prays to God - just in case. I'm not a perfect-histogram monger, but I do like to know the deal, in case I change my mind later. Paul's RGB separation curves are a fairly radical adjustment for an 8-bit image to undergo. Not unduly so, but if you've already stressed an 8-bit file on the way, these curves won't help the case. So far, I haven't noticed that working the file all the way through to print (including the application of Paul's curves) in 16-bit gives any better a print, but that is perhaps another topic. Those who participated in the PiezoBW 30 print exchange know that Ron Landucci, Paul Roark, and Jerry Olsen, contributed prints using Paul's VT method, and curves, that were at least the equal of any prints in that exchange. Thus, my question is somewhat theoretical, but I'm trying to get my head around some of these concepts. Is a grayscale workflow, going through the PiezoBW profiles, and the PiezoBW RIP, more gentle to the tonal data (bits) of a file, relative to an RGB file, with RGB separation curves, and the Epson RIP (driver)? Is Piezo somehow getting around separation curves, or are they just contained in the profiles? BTW, is that all profiles are - a curve set? Somehow they seem to be doing a kind of "selective color" treatment, which seems a bit more complex than curves, but that's just based upon my observation, I know nothing about them. Todd