Color Control: Work in Process

Color management—that is, printing the color(s) you thought you were going to print—is achieved via process control, or the measurement of production control targets to maintain consistency and predictability throughout the print manufacturing cycle.

"If you don't have process control for the press and in prepress, color management won't work," says Dan Remaley, a specialist with the Process Controls Team at the Graphic Arts Technical Foundation (GATF), Sewickley, Pa. Remaley traverses the country for GATF and the International Prepress Association versing graphic arts professionals on the ins and outs of controlling color variables, from scanning and film output to proofing and press.

Says Remaley, process control is precisely where the problem lies. "The bottom line is that printers don't measure their print attributes; instead, they're using solid ink densities to determine whether they're printing correctly or not."

Remaley, in addition to working as a press operator, color stripping supervisor, and production and plant manager, spent 14 years at a high-quality trade house producing film and color proofs for printers and advertising agencies. It was there that he established measurable process control and training standards, and served as the sole troubleshooter when color proofs and press sheets didn't match.

He learned that solid ink densities are not what printers ought to be measuring. "The primary telltales," he says, "are dot gain and the gray balance characteristics of the print."

GATF studies confirm that the most significant color balance shifts occur when the dot gain is out of balance or diverges between colors during the press run. Dot gain ideally should be the same for all colors, states Remaley.

There are, says Remaley, some readily available ways for printers to improve their process control, and thus their management of color. Of all the tools listed in GATF's 2001 Process Controls Product Catalog, including plate control targets, color bars, and GATF/SWOP proofing bars, Remaley contends that the Proof Comparator is the most valuable. It measures solid density, dot gain, gray balance, hue/gray error, print contrast, and resolution. "But it's a hidden secret," he says. "Nobody uses it."

The other "hidden secret" Remaley exhorts printers to adopt is Gray Component Replacement (GCR), the process of removing multicolor gray, the dirtying component of a color, and replacing it with black. For example, a red that before GCR contained 100% magenta, 80% yellow, and 20% cyan would after GCR comprise 100% magenta, 80% yellow, 10% cyan, and 10% black.

"GCR allows printers to put black into areas where three colors print," explains Remaley. "Three colors printing produce a neutral color. With black supplementing, I can reduce the values of those three colors. For example, with GCR I could change a 50% cyan to maybe 30%, and change 40% magenta and 40% yellow to 20% apiece and then add 10% black. I've simply made 30% dots of those 50% dots, which don't change on press as fast. Creating this wider window gives the pressroom more opportunity, yet most people don't even know about GCR."

Recently, QTI unveiled its Color Control System, a closed-loop press control system that was designed through an alliance with Swiss software firm System Brunner. "I think this really is quite a revolutionary product," concludes Remaley. "This is how color should be run but never has been." The system is capable of in-line measurement of gray scale and CMY midtone reproduction as well as color density for web printing. Essentially, the color bar measures three-color gray and opens and closes ink based on three-color gray.