Color management part 2--press fingerprinting

Press fingerprinting for color matching lays the groundwork for a collective color vision.

WHEN YOU MAKE most of your living writing about technology, you have the privilege of picking the brains of some very well versed subject-matter experts. Opinions vary of course, but I've found that the most impassioned, most expressive leaders all have one thing in common: Vision.

A motivational speaker once told me that it was vision with a capital "V" that made it possible for U.S.-born Gertrude Ederle to become the first woman to swim across the English Channel in the 1920s. She described how each time Ederle started to falter along the grueling 21-mile crawl through icy waters in gale winds, her coach would show her a photo of her landing site. By keeping a very specific pictorial reference of her goal in front of her, Ederle not only conquered the Channel, she beat the best men's time by two hours.

I never forgot this inspirational anecdote, and I thought it would be an appropriate lead for an article that takes us through somewhat unchartered waters. Vision, both literally and figuratively, factors heavily into our mastery over color in printing. For while technology has given us a methodology and means for getting at the DNA of color (packagePRINTING September 2003, p. 12, "To Measure is to Know"), the ends to which we apply our knowledge is determined solely within human minds and judged ultimately by human eyes.

As suggested in last month's article, a color-managed workflow is one in which every color input and output device employed in the print production chain has been a) calibrated to its optimal performance under a given set of repeatable conditions; and b) has been profiled and is capable of employing industry standard ICC color profiling data.

Color management software is used to direct the color transformations of an image from one device gamut through to that of another, in an attempt to make two outputs match. They're also used to edit and adjust the numbers of a device profile.

The International Color Consortium (ICC) publishes a format specification for color profiles, which describes how color data is to be expressed. Software developers and manufacturers of color input and output devices use these specifications. The ICC also publishes a registry of reference names for color profiles—which could grow to be of major importance as the industry embraces the need for a common color language.

There's no law that says the color profile has to be an ICC standard format, though ICC-compliance is highly touted, and the electronic printing community has clearly expressed its desire for a standardized approach to communicating color. David McDowell, a visionary from Eastman Kodak and the NPES, has written a brilliant description of how the graphic process could evolve using universal data exchange protocols ("Then & Now!," IPA Bulletin, July/August 2003). McDowell spends considerable time discussing the implications and issues concerning what is surely the most important punch point—creating an acceptable model for color approvals.

Another visionary who works with press fingerprints and profiles every day puts it this way: "At some point it will always come down to a single person saying 'it matches.'" This implies, of course, that color is still highly subjective. And it is. For when we examine the practicalities of profiling a printing press, we see there's plenty of room left for old-fashioned human ingenuity and a certain amount of eyeballing.

Using the basic principles of color-managed workflows, we could create a predictable press-to-proof approval environment by:

1. Establishing the optimal running condition for a specific press for a given set of inks and substrates (calibrating);

2. Manually and electronically cataloging key measurements from the press (profiling); and

3. Applying the profiling data to modify the output from calibrated and profiled color proofers, filmsetters, and platesetters (separating, screening, distorting, etc.).

The shear number of ink/substrate/press combinations in package printing makes the term "fingerprinting" somewhat of a misnomer—there's no such thing as only one possible fingerprint per press. That's where averages are often used as a compromise and a place where some standards can help. For example, for years the commercial printing world has characterized a whole body of installed presses running to SWOP specifications under some generic sets of data.

But calibration at its utmost means that the press has been brought to its best performance under a given set of circumstances. And that changes with everything from press speed, ink dry rate, screen ruling—no need to go on. So, who determines the baseline? Who establishes the target, or "aim," as McDowell calls it?

And who determines the critical measuring points to catalog? How and where will the catalogs be recorded and stored? Will a printer be able to offer his fingerprint to any separator with the assurance that he'd only see proofs that matched his press capabilities?

It would be interesting to see how the visionaries in your company are answering these questions. No doubt the specifics are what make up some of your unique blend of color expertise. The specifics also speak volumes about relationships between print buyers/specifiers, imaging service providers, and printers. They offer a glimpse at a possible collective Vision for a color-managed packaging workflow of the future.

by: Terri McConnell