Last week I wrote about a problem I was having getting good prints of my Apollo/Soyuz in Floodlights photograph. You can read that column here; the condensed version is that I couldn't get the flood light beams to print out with smooth and even gradients unless I turned off color management and handed over the rendering to the Epson 3880 printer driver.
Several readers suggested that this was a problem with out-of-gamut colors, an idea I rejected because the gamut preview in Photoshop told me that everything in that photograph was well within my printer's color range.
Well, I'm un-rejecting it. And therein lies a curious and important tale.
Mike Chaney, of QImage fame, kindly agreed to look at the file and see if he could figure out what was going wrong. He observed that when he previewed the gamut for a different printer that he happened to have, he did see out-of-gamut colors, something like the preview above. Their locations aligned pretty well with the harsh breaks that I was seeing in my print's rendering. I brought Dave Polaschek (the printing engineer on Photoshop) in on the discussion, and the three of us batted it around for a bit, for, you see, I still wasn't seeing any evidence of out-of-gamut colors in my previews.
I still don't know for certain that there are out-of-gamut colors in that photograph for my printer. There's no test that I or Dave or Mike can run to determine that for certain. But it looks like a duck. And it quacks like a duck. And there are webbed footprints in just the right (or wrong) places. So we think it's a duck.
This is important because it means I can't entirely count on gamut previews to tell me if all my colors are properly printable. Neither can you. Most of the time it works pretty well. For this photograph, it failed very badly.
Does it squish?
Why doesn't gamut preview work like it's supposed to? It lies in the problem of rendering out-of-gamut colors in a pleasing way on a printer. Color films and decent digital cameras can record colors that no printer can print. Furthermore, an RGB color space like your display uses isn't a one-for-one match with the CMYK color space a printer works in. There are colors your monitor can display that can't be printed. What do you do about those colors? Well, it's that problem of squeezing a pint into a 12-ounce can, again. The only way everything is going to fit is if something squishes. Colors in your photograph that fall outside the ones the printer can print get mapped into colors that it can print.
Without getting technical about it, the software that creates the profile that color management uses has to make some assumptions about how that mapping occurs. For the sake of computation, it also has to treat some out-of-gamut colors as if they were in gamut so that it can deal with them at all. Consequently, there is not really a clear and accurate boundary in the profile or in the gamut preview between colors that are in gamut and colors that aren't. The boundary is fuzzy.
The printer, though, doesn't think so. If it gets thrown a color to print that's outside its comfort range, it will print something, but it may not do it very well. ICC profiles don't understand a particular printer's idiosyncrasies very well. The printer driver is more likely to be written to take into account said printer's foibles.
Most of the time this kind of situation won't jump up and bite you. It bit me good in this photograph. I can think of a few others I have that I've yet to print successfully where I think the same thing may be going on. I'm going to try printing them with color management off, letting the printer control color, and see if it works better.
If profiles can cause problems like this and give misleading results, why not just avoid them all the time? Because 99+% of the time, profiles won't cause problems like this, and they will render in-gamut colors much more faithfully than printer-managed color will. Printer-managed color will not produce superior color most of the time.
As I wrote previously, if you consistently get better results from printer-controlled color then full color management, something's wrong with your system. Either with your profiles, your software, or how you're using them. I can't help you fix that, I'm afraid. All I can do is give you the heads up. On occasion, though, printer-controlled color can save you from a nasty boundary condition failure.
Ctein's regular weekly column appears on TOP on Wednesdays.
Note: Links in this post may be to our affiliates; sales through affiliate links may benefit this site. More...
Original contents copyright 2011 by Michael C. Johnston and/or the bylined author. All Rights Reserved.