This is post three in a series about my experiences in publishing a book. The series starts here.
In the 90s, when I was working at IBM as a color scientist with a special interest in color management, I worked with engineers from Kodak, Adobe, Xerox PARC, Apple, and hp on what we called in those days device-independent color. We all seemed to share a common vision of the future. You’d do your editing in some colorimetric color space, and then send the file, tagged with a profile to indicate its color space off to a display, or printer, or printing press. Before it got rendered, software would look at a color profile for the output device and at the file’s color profile, then it would map the colors in the input file to the colorants (electron beam currents, inkjet dot counts, whatever) of the output device, mapping colors outside the gamut of the output device according to rendering intents specified in the input file.
That’s pretty much how it works today for inkjet printing. Hold that thought.
In the 90s, there were several ink systems introduced that supplemented the traditional four offset printing process colors, cyan, magenta, yellow, and black (CMYK) with other colored inks. One such system was developed by Pantone and called HexaChrome; the two added colors were orange and green. The press that Hemlock is talking about using for my book is a six-color press.
My Epson 4900 uses orange and green inks to extend its color gamut.
Based on all that, I thought that Hemlock would supply me with a profile for their press so that soft proofing in Photoshop and Lightroom would work right, that they’d use six process colors, and that I’d send them files in my preferred editing color space.
Wrong on all counts.
First off, Hemlock uses only four process colors. The extra two inks that could be used in the press are for spot colors. Second, they want the files in CMYK. However, it’s not the CMYK native color space of the press, it’s a standard CMYK space that comes with Photoshop called “Coated GRACoL 2006 (ISO 12647-2:2004)”. It’s unlikely that the native space for their press and whatever paper is in it is exactly that standard space, so they must be tweaking the press so that it matches the standard. This turns color management on its head; rather than converting the colors in the image to colorants using a press profile, Hemlock is making the colorants of their press match those of a standard profile.
Poking around the web, I find that what Hemlock is doing is common. Not universal, certainly, but common. This scheme gives up some press gamut in the interests of standardization, but has the (small, I would think) advantage that they don’t have to distribute color profiles. It also finesses the issue of how to ensure that the gamut mapping software of the customer is executing the same algorithms as the gamut-mapping software of the printer, since the printer isn’t doing any gamut mapping.
In the case of Hemlock, they want the images in Coated GRACoL 2006 regardless of which paper and paper gloss I specify, whether we’re using 10 micron or 20 micron plates, and whether the images are varnished or not. All those things will influence the color gamut of the printer/paper combination, and will affect the mixture of colorants necessary to get any in-gamut color in the output.
This is not a color-managed workflow on the sense that we color engineers envisioned it 20-some-odd years ago! Hemlock must be counting on tweaking the press to get close enough.
Well, I’ve seen their work, and it looks very good indeed. I’ll proceed ahead expecting that mine will, too. However, this whole scheme gives the engineer in me more than a little nervousness.
I thought I’d export a bunch of files from Lightroom in the Coated GRACoL 2006 color space. Can’t do it. Lr doesn’t support any CMYK spaces for export. I wonder why they have this limitation, since the color space conversion can be done with the same Adobe color engine that handles color space conversions in Photoshop. The cynic in me says that they did it on purpose, since CMYK = pro, and pro = able to pay more, and, when you put the two together, it means that Adobe thinks that anyone converting to CMYK ought to pony up and buy Photoshop.