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Rich Black Formulas

Why Solid Black Isn’t Exactly Solid—and How to Plan Around It

BY KEN MORRIS

When we look for clarity in conversation or concept, we use interesting terms.

We say something is either black or white. If something is morally ambiguous, we say it falls into a gray area. And, while we may remain neutral on opposing opinions, in reality, neutral shades present their own biases.

I recently read that traditional Japanese geishas with stark, white face makeup will cover their mouths when smiling in what presents itself as a demure act. In actuality, it has more to do with teeth appearing yellow in contrast to the makeup.

That white is not an absolute is well known in the world of paper. Lay a sample down by itself, and it appears perfectly white. Lay another brand sample next to it, and you’ll likely notice a difference in hue, one appearing yellow because the other has had bluing agents introduced during its manufacture. And, in coated stocks, if you are looking at differences in grade number, you may be observing a difference in brightness, making a stock that appears white by itself look slightly gray in comparison.

Neutrals are anything but neutral.

With inks, it’s easy to see differences in gray hues. Greys can either skew warm or cold depending on the pigment formulation. A finger stroll through the gray section of a Pantone swatch book will reveal a myriad of greys, not only in shades of brightness, but also in leanings of color.

But, what about black?

Black has always tended to represent itself as an absolute. It is the absence of light. It’s an abyss of reflected or transmitted wavelengths. In everyday life, it’s a dark living room with furniture for your toes to find. And, in printing, it’s—well, black. Or, is it?

A Primer on Printing Inks

Let’s go back to basics for a moment. If you’re a seasoned design professional, you’ll be well familiar with this. Humor me.

For a moment, take a look at the color wheel. Not the traditional ROYGBV color wheel they taught you in art class, but the one for the designer’s world, the RYGCBM wheel, incorporating RGB and CMY (for the moment we’ll leave K, or black, out of the mix). The red, green and blue gamut—device specifics aside—represents the primary colors of light, or additive colors. Cyan, magenta, and yellow are the primaries of pigment, or subtractive colors. When you add RGB transmitted light together at full intensity of each, you get pure white. When you add solid values of cyan, magenta, and yellow pigment (reflecting light and absorbing certain wavelengths as it reflects—thus, subtractive) printing over each other, you get perfect black—theoretically.

There is, however, a difference between theory and practice. First, offset printing inks have a transparent nature. Even inks that carry an “opaque” designation aren’t totally opaque. And, when you add solid primary inks together, the buildup of transparent inks at best yields a muddy, murky gray approximating black.

This is where adding “K” comes into play in the process color world. At its most practical, black ink gives you something to print text in. With color images, however, it saves the day by adding contrast. While, technically, a designer could reproduce color photos using only cyan, magenta, and yellow inks, dark hues suffer without applying black in the shadows.

There are levels of technical know-how on how black works with CMY for those who want to dig deeper (GCR, UCR, etc.), but for most designers on a production schedule, Photoshop standard color settings—like “U.S. Web Coated (SWOP)v2”—set for RGB-to-CMYK conversion will take care of you when you convert your images. Usually, the amount of black ink in your CMYK file isn’t something you have to consider in the normal world of print design. But then, there’s the matter of designing with black elements in the process color gamut.

The danger here is that a reasonable design professional at this point could sit back, frown, scratch his or her head, and think, “I design in black all the time. What’s left to learn?” And, that would be a reasonable question except for the number of files printers get from experienced designers and advertising agencies with atrocious disregard for issues dealing with process black mixes and ink coverage in the file.

Designing in color with black

There are two considerations for the quality of black coverage in print design elements: aesthetic and practical.

Aesthetically, it comes down to relativity—the quality of dark or black areas in a color image compared to surrounding black design elements. If you are designing a black-ink-only layout, you have nothing to worry about. The darkest, 100-percent-coverage area of a photo is going to match the solid black design elements within the boundary of the page. The difficulty comes when color elements are introduced.

Process color images that are converted from RGB to CMYK using SWOP (Specifications for Web Offset Press) settings—pretty much the offset printing industry standard—will find the darkest image area consisting of nearly 300 percent ink coverage (Open your Photoshop Info palette, set your cursor crosshairs on what looks like absolute black in the image, and you’ll likely find values around 75C/68M/67Y/90K). If you are working with a layout where the photo is surrounded by process-mix color elements and black text, everything is routine. If you’re going to use large areas of black near the photo—sidebars with reversed text, large black display areas, large bold black display type, etc.—using just 100 percent black won’t do. Rather, it will look washed out in comparison to the dark hues in the photo.

Remember, all inks are transparent—including black ink. When your design requires black display elements next to process color images, especially those that have significant deep hues, consider using what is called “rich” black.

Rich black, poor black…

The formula for rich black varies among designers and printers. Usually, it falls somewhere around 60C/50M/50Y/100K—260 percent Total Area Coverage (TAC). What you are looking for in a rich black formula is significant buildup in the three primaries to construct a neutral base medium gray hue upon which to add solid (or near solid) black. The combination renders a deep black hue that matches the deep tones on an adjacent color image from process ink buildup.

Further, rich black should have a slightly higher cyan component. By pushing the cyan, the black mix is forced toward a slightly cold hue, which renders a more neutral black perception than a purely neutral, equal-component underlay of primaries under the black. And, since acceptable variances on press can approach as much as 4 percent on any of the four colors, hedging the cyan by 10 percent insures that the black tones will be consistently cold, even if the yellow ink creeps up by 4 percent in the course of the press run.

Another, very important aesthetic consideration for building four-color black on your layout is the sheen that ink buildup produces on the press sheet, especially on a heatset web press, and especially when printing on matte or dull stocks. One of the wondrous things the oven of a heatset web press does for inks as they pass through is impart glossiness to them. That makes for a very nice juxtaposition between the glossy design elements and the flat white surrounding stock. You do need, however, multiple layers of ink to accomplish the look, and simply placing a 100-percent-black design element in the same area as a heavy-coverage process image will not give a commensurate finish. Rich black will give you what you’re looking for.

And now, for the practical consideration…

Bear in mind that as in many things in life, you can have too much of a good thing.

Remember that SWOP standards allow for a maximum total area coverage of 300 percent? Well, one could ask, if building process ink coverage in rich black is so important, why not go for 100 percent of all four colors—or 400 percent total coverage?

There is a selection in the color palette of most desktop publishing applications for “Registration” that prints 100 percent of all colors in the layout—in a process color layout, it renders 400 percent coverage. It’s intended for those hairline registration marks around your layout so the pressman has something to check for alignment.

Please don’t use Registration for rich black.

If you do, and the project makes it all the way to press, the pressman will likely pull the job. The reason for the 300 percent maximum coverage spec in process images is that presses usually can’t handle more TAC without a myriad of problems revolving around ink that refuses to dry. On a web press, this can be a huge problem. On uncoated stocks it can also be a huge problem (I’ve seen 400 percent ink coverage actually seep through 50 pound offset stock!)

You should be familiar with your printer’s preferred color settings. He knows what the presses are capable of and where the limits are. If you aren’t—if you’re simply relying on Photoshop/SWOP defaults (while you’re probably safe)—you should pick up the phone. Some printers will allow a few percentage points heavier coverage, and some need a lower TAC target.

Another thing to consider is how your printer’s trapping software treats the black-ink components in your layout. If, for example, you place a wide black-ink-only bar over a full-page color subject to reverse out a title, you may be able to see the four-color subject through the bar—and some proofing systems won’t catch it: you may not see it until you’re on press. Remember, the black ink is transparent, and the trapping software many times will simply surprint, or overprint, all black ink without knocking out the artwork behind it. Rather than making it a trapping issue, simply use rich black in the bar. The trapping software will see another color element and neutralize the four-color image behind it.

Make things match

There are scenes in old (and some new) sci-fi movies where you’ll see some guy in the cockpit of his spaceship and something unnerving is happening—the black of the darkest shadow area of the cockpit doesn’t match the black of space outside the window. The cockpit was shot against a “green screen” and “space” was added later, and the post-production crew didn’t take into account that the two should match. In the meantime, I’m sitting in the theater biting my nails, and not because of the suspense.

The same thing happened with a magazine cover I saw once where a photo of the Earth in space was suspended on an extended black cover, and there was a viewable difference between the blackness of space and the black background. I had the same reaction I had in the theater.

It would have been simple enough to sample the blackness of space in the photo, get the CMYK formula, and build that color in the palette for the background—as long as the TAC doesn’t exceed the printer’s maximum ink limit.

Lastly, on black type…

Please don’t use the rich black formula for text type. You would be surprised how often files come into the printer’s prepress shop with 11- or 12-point text marked as rich black or registration. When four-color text goes on press, the slightest registration hiccup that wouldn’t be an issue in a photo will create a process-color halo around the edge of those black text characters. And, especially if your rich black formula includes black screened at 90 percent or so, your text characters will have a halftone screen when they should be solid. Just use black only for your text type—that’s one of the reasons it’s there.

Ask the printer

Printers usually have a good idea of what makes a good rich black formula. It’s still a good idea to have your own, though as long as you are aware of the caveats.

Always bear in mind that neutrals simply aren’t neutral, especially in the world of process color. White isn’t simply white among paper stocks, and black isn’t simply black among inks. And, as is the case in many moral dilemmas, there are many different ways to arrive at gray. ⊗

©2008 Ken Morris

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