Mastering the technique: Gray Component Replacement - Folio: Tech Trends: includes related article

Mastering the technique: Gray Component Replacement

Production managers have the demanding duty of coordinating a host of suppliers, and they quickly learn that they must understand each vendor's specialty well enough to ask the right questions and give a few answers of their own. Nowhere is this need for technical knowledge greater than in utilizing the Gray Component Replacement technique in color separations. Gray Component Replacement (GCR) is a relatively recent approach, and work here is further complicated by the lack of application standards. This article will acquaint you with the technical basis for GCR and offer some guidelines for applying the technique to your color reproduction. You'll find that your mastery of the concept is vital to integrating your suppliers' contributions.

GCR and color reproduction.

Get a few production people together and you'll hear GCR called everything from a brilliant breakthrough to smoke and mirrors. The former opinion takes note of the clear value of the principle, and the latter reflects the wide range of results achieved without standardized specifications. Let's look at the benefits implied by the concept first.

In a separation made with the Gray Component Replacement technique, the neutral color element of each tone is made with black ink instead of a neutral mix of process colors (see sidebar for details). As a concept, GCR is clearly a wise approach to color reproduction. It should yield purer hues because the darkening is produced by a neutral black instead of a trace color. Further, since ink is a wet film applied at great speed in printing, anything we do to limit the problems inherent in trapping translucent inks will improve reproduction. In GCR, we use less black ink than the process ink we're replacing. Finally, we're building color in a theoretically more stable manner.

When we eliminate the process yellow as the gray component in a blue, all the adjustments made to yellow on the printing form overall have no effect on this hue. At an extreme, we've greatly reduced three-color overprints in every area except for the browns we're seeking froma full yellow, magenta and cyan mix. Although there are few tones in a color original that can be broken down without some use of all three process inks, we've eliminated some and reduced the trace amounts in all others. Practically speaking, we should achieve easier color adjustment on press since we'll tend to jocky black and two colors, not three, for major corrections.

Benefits in practice

If GCR earned its pie-in-the-sky reputation for any good reason, it's because early proponents of the technique promised printers greatly reduced ink consumption and lightning-fast makereadies. In practice, GCR is not quite this godsend. In large part, a GCR revolution can't take place as long as magazine publishers include ad pages produced by the chromatic method. Even if all the editorial color on a form is created with GCR, the random conventional ads will continue to demand ink consumption and color correction in makeready as they always have. However, we have learned that combining chromatic and achromatic separations poses no problem of its own.

The process color inks are more expensive than black ink, and in theory the reduction in process inks from GCR should yield real dividends to magazine printers and publishers. In fact, printers so far are not reporting any measurable savings. There are at least two likely explanations. First, GCR can be applied at any intensity, and when used cautiously it will not convert much process color to black. Second, it's been suggested that the greater color stability of GCR separations inspires pressmen to increase ink levels overall to improve the brilliance of ads and GCR subjects alike. Whatever the reason, printers are not tripping over themselves to offer you ink consumption discounts for GCR separations. In time, the benefits in ink reduction may be more apparent, but even if you're buying ink by the pound instead of the page, you may see little savings.

GCR would simplify makeready if it were not for the array of pre-press vendors represented in any given magazine signature. Between the usual inline conflicts and variations in proofs, your editorial color may fight with ad separations to keep the makeready process the same struggle it's always been. A catalog publisher is in the best position to reap the benefits of a speedy makeready because he can utilize GCR in all the separations. Magazines can't take such an all-or-nothing approach.

Nevertheless, some printers report substantial improvements in makeready time when GCR is used in editorial work alone. When all is said and done, any procedure that helps a printer reach acceptable color sooner is going to obtain support. Although some printers haven't found any particular improvement in makeready with GCR, the proponents of the technique mutter that these unconverted souls simply haven't been exposed to proper GCR. As we'll see, it's not simple to define proper GCR, and GCR zealots are to be forgiven for assuming that unimpressed printers have simply worked with unimpressive GCR.

During the run, we can reasonably expect that color will remain more stable. Not only have we reduced the constituent parts of a hue, we've curtailed the potential for variations in color from dot gain. However, as you'll see below, dot gain remains a serious problem for GCR color. Although we've reduced the number of colors that may alter a hue through dot gain, we do face gain in black. Nevertheless, a GCR signature tends to hold color and require less adjustment while on press.

Overall, GCR is not a way to reduce costs but a way to improve quality. It hasn't swept the industry as an economic boon, although it does have some functional savings built into it. Rather than looking for cost reductions from GCR, production managers are advised to savor it for its ability to improve quality at no additional cost. If you end up with the same ink bill but all your color separations are bright and brilliant from the extra ink lavished upon them, you can still count yourself ahead. And if makereadies consistently go a bit faaster, you and the printer both benefit by saving the magazine sooner, even if the printer isn't comfortable enough with the procedure to pass some savings on to you.

Additional benefits

The basic move of replacing the gray component of process color with black ink has some further advantages, chiefly of interest to your printer. In theory, the thinner ink film that GCR permits allows successful presswork on lighter-weight paper. But as noted previously, a net reduction in ink may not always occur with GCR. Along the same lines, faster drying times are theoretically possible with less ink to dry.

Whenever we can make one of those pesky brown tones with two colors and black instead of three, we take a giant step toward reducing distracting moire patterns. moire is most evident with a great concentration of large dots of similar size. When we change the balance by reducing or eliminating one of the process colors, the familiar rosette texture of a separation is made a good deal more subtle.

In sum, GCR seems to have numerous benefits. Even if it isn't saving anyone huge amounts of money at the moment, it certainly permits improvements in quality at no increase in cost. When all is said and done, converting the gray component of a hue to a neutral black should yield a purer color that is easier to control on press.

The downside

Right now, any printer or production manager who wants to appear extremely knowledgeable about GCR clucks his tongue and tells you about the wait-and-see attitude he's adopted about the technique. Plenty of GCR subjects are being printed every day, yet no printer or separator can confidently tell you that the process is under control. There are two reasons why: the variations in the amount of GCR adjustment among separators, and the lack of specific proofing controls.

A color scanner is a very obedient device. We can set it to read light intensity and compute a host of values in response. When equipped to produce GCR color, the scanner reads the gray component on a hue and performs calculations based on the operator's settings to replace a process color with black. We actually don't want too much of a good thing, so we won't let the GCR process run at 100 percent; we'll throttle it back depending on our paper and printing process. Whereas a newsprint product might use 90 percent GCR, a magazine on grade 5 coated stock would tend to use 70 percent to 80 percent GCR. These percentages mean just what you'd assume: We're replacing 70 percent to 80 percent of the gray component with black.

Under the benign printing conditions of most magazines, GCR should be limited to avoid allowing too much black and too little color definition in shadow areas. But it is here that trial and error must really begin. Many printers have advised their customers that using anything less than 65 percent GCR represents virtually no change from the chromatic process, and that real dividends begin only with 70 percent. Each publisher's range of subject matter must play a part in determining the proper extent of GCR adjustment. There is no substitute for on-press testing when determining a GCR specification.

Testing's fine, but why can't a proof help us evaluate the process before we commit to paper? Only a proof or a pure test sheet lets us compare different specifications side by side. Within the magazine, we can only print our regular subjects and note whether or not they look relatively decent; we can't compare a range of GCR adjustments. To make proofs more useful here, we might want separators to include a test target of color overprints. Such targets are already used to evaluate gray balance and overall color. If we had one set of targets representing some chromatic three-color overprints and a second set designed to yield the same tones with GCR in effect, we could examine a proof as developed to see if the black was contributing what it should. Of course, the only way to examine the black directly is to use an unlaminated proof, such as a Color Key. In the early stages of your GCR program, you might well want to make some Color Keys simply to see the radical change in your separations firsthand.

Although test targets would help us see that proofs were processed properly with GCR in effect, we'll still have trouble anticipating the printed effects of different amounts of GCR. Call it mysterious, but we can obtain similar printed effects from a host of different film specs. More important, two proofs that look identical may print quite differently when dot gain and particular color corrections come into play. In short, we lack a proofing system that accounts directly for GCR, or allows us to evaluate GCR completely before printing.

The lack of standards for GCR amounts or proofs obviously holds back the printing industry. As a production manager, you'll want to note that the separator makes all the changes while you and the printer reap all the benefits. It's not surprising that separators have gone as far as they have to advance this technological improvement, since they can satisfy you with better results. But until printers and separators feel confident about the other's contribution, we won't see the GCR standards we all need.

Other technical flaws

Even if we do arrive at standards for GCR use, there will still be three problems that limit the quality of GCR reproduction. First, our reliance on black ink brings two nasty side effects: black shows the greatest dot gain and is thus the most unstable color, and black must remain as even in density as possible to keep text from varying from black to gray. When black is used to color correct, it can, at an extreme, vary enough to undermine consistent type density. However, even though a great deal of black is used in GCR, it should behave as a neutral tone, and not be used for excessive color correction.

The dot gain issue is more serious. Color separators working on GCR specifications must be alert to the need to compensate for dot gain. Simply increasing the amount of black will not do the job properly: It must be increased with compensation for gain built in.

The second troubling matter is the problem, perceived or real, in reproduction of certain light tones with GCR. In the abstract, a pastel tone might be reduced to two colors plus black, without an adequate trade of the third process color. This could lead to weak color, with less brilliance than possible by the chromatic method. Caucasian flesh tones are particularly susceptible to deficiencies here. According to one printer, this concern may be exaggerated, but the basic problem will still require consideration. Reducing the gray component equally in every tone may not yield good results, and some adjustment for the relative saturation of a color may be necessary. In one printer's opinion, you may see no advantages from GCR in light tones, but you won't see additional problems, either.

Finally, we face the need to develop tone curves unique to the GCR method. A tone curve places the shadow tone, quarter tones, and mid-tone at particular densities in order to compensate for the inherent compression of the tonal range in printing. Since the black negative will now shoulder a very different burden, this tone curve must reflect the reality of dot gain, the new contribution of black, and the need to position highlights and shadows for a balance of detail and contrast.

As you can see, instituting GCR is not a simple matter. You must work with your printer and separator closely, sometimes acting as the impartial voice of reason when reproduction problems emerge with GCR as the scapegoat. If all of you tackle the program jointly, you can rely on each other's expertise to produce results of high quality. This will entail special care in making and interpreting proofs, compensating for dot gain, and monitoring the problems of shadow detail and light colors.

Among other things, your separators is likely to make a further adjustment called UCA, or undercolor addition. In straight GCR, the density in dark areas may be artificially reduced, yielding weak shadows and reduced color intensity. Some compensation for this lack of gloss is required, and a properly implemented program of UCA should correct the deficiency.

In the last few years, quite a number of separations have been handed over to printers as GCR that were in fact little more than lightly adjusted chromatic separations. A great deal of confusion and disappointment resulted. At minimum, make certain your separator is using GCR with enough intensity to make the technique worthwhile. Overcautious GCR gains little. Use an unlaminated proof to gauge how effective the GCR is. You should see virtually no cyan in a red and a great deal of black everywhere.

In the end, GCR promises superior reproduction. It's up to us to follow through and make that promise a reality.

Alex Brown is president of Printmark, a magazine management and production consulting firm. She has been associate publisher of Small Boat Journal and Hemmings Motor News.

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