Ed #5 Enhancing Color

“Less is more,” said Mies van der Rohe. But in the graphic arts, more is often better, especially when it comes to color. More color gives you more ways to communicate, more ways to make an impact and better ways to match the color of the original. And more is easier to get than ever before.

Conventional four-color printing has been the top of the graphic arts food chain. Light passes though transparent inks of the three subtractive primary colors—cyan (C), magenta (M) and yellow (Y)—strikes the white paper and is reflected back to the eye through the colored ink film. The cyan pigment absorbs red and reflects, or transmits, blue and green light; magenta absorbs green and reflects red and blue, and yellow absorbs blue and reflects red and green. Black (identified by the letter K) is added to enhance the depth and extend the tonal range of the colors.

Intermediate colors—colors other than the subtractive primaries—are formed by laying one film of transparent ink over another. Applying cyan over yellow, for example, will produce green because the cyan ink absorbs the red part of the light and the yellow ink absorbs the blue portion. Only the remaining third—green—is transmitted back to the eye.

Combined in various percentages, CMYK inks can reproduce thousands of hues and mimic the look of continuous tone images such as color photographs. But four-color printing is not full-color printing. Because only three colors of inks are used and because even the best printing is not 100% accurate, conventional four-color printing can only reproduce approximately 100,000 distinct shades.

While that might seem like a lot, it is far less than the number of colors, said to be anywhere from 1 million to 10 million, that can be distinguished by the human eye. Oranges, greens and purples, intense shades of any color, and metallic tones can be especially difficult to capture using the four process colors. And process colors often cannot create a perfect match for solid colors, such as those used in corporate trademarks or on corporate letterheads.

Until relatively recently, the most common way to correct such drawbacks was a second pass—sending the project through the press twice. On the first pass, the press might print the four process colors. Then a second pass might be used to apply special colors, varnishes or screens. The results of using a second pass can be spectacular, but the process is time-consuming, expensive and challenging. Press times double, along with the possibilities for errors, and unless the paper is held in exactly the right position, or registration, images can appear cloudy or out of focus.

Within the past decade or so, however, doing more with color has become increasingly common. A growing number of presses have five, six, or even more printing units, so four-color printing is, increasingly, just the start. Printers can now offer a greater range of colors—and special effects—with one pass through the press. And that means that designers can produce more powerful layouts, do a better job of matching difficult originals and capture colors that have rarely been printed before.

So how do you make the best of these evolving capabilities? Now that extra units are available, what do you do with them?

The most common use of an additional unit is to apply a special spot color or varnish. While the four process, or CMYK, inks, can produce a wide range of colors, they cannot produce all colors. So sometimes a spot color, applied as a solid and not as a screened tint, is used to provide an exact match of a corporate trademark, for example, or to create a screaming fluorescent yellow headline.

Applying varnish is another common application for an extra unit on the press. Varnishes, which are available in gloss, satin or dull finishes, are applied just like a solid ink. Varnishes can be spot applied precisely where they are desired, to create a variety of effects. A gloss varnish can help give a “wet” look to a photo of water, for example. Covering the background of an image with a dull varnish and the image itself with a gloss varnish—a step that would require two additional printing units—can increase contrast and help make the image leap from the page.

For more on varnishes and other coatings, see Ed #4

The additional units found on many presses can be used in other ways as well. Touchplates, which are also known as bump plates or kiss plates, apply an additional screened color to an image or a portion of an image, to increase, or bump up, color saturation and contrast or reproduce a color that is hard to capture using only conventional process inks.

Touchplates are often used for images with vibrant reds or blues, such as a child’s red wagon or a deep blue sky, or in images with a wide range of hues that may lie outside the range, or gamut, of CMYK colors. Using a screen of the bright color you want to match along with CMYK inks adds to the intensity of the color and reveals more highlights. Applying an extra hit of black can deepen the contrast of the image. A touchplate of a metallic ink can help bring out the shine in jewelry or metal. A touchplate using a fluorescent ink can add an otherworldly effect to the image.

But there are good touchplates and bad ones. Because touchplates are most often used on a portion of an image, they need to be carefully blended in with the contours of the original—otherwise, the touchplated area will look like a cutout. Good touchplates also match the full tonal range, from light to dark, of the original image. Remember too that not all of the colors, such as metallics or fluorescents, that might be used in a touchplate can be accurately reproduced with current proofing systems. What you see on the monitor may not match what you see in the proof or on the press.

Sometimes, it’s possible to achieve many of the same effects as a touchplate without using any additional units on the press. Instead, one or more of the conventional CMYK inks are replaced with different inks—anything from a more intense shade of a process color to four fluorescent inks. The switch can help to highlight a specific area of the image by making the dark blue waters of a lake even bluer, for example. But because the color is applied in place of a process ink, all of the image will be affected by the change, raising the risk of sickly skin tones and other unintended consequences.

Most of the more-than-four-color work produced today relies on manually created bump plates and custom inks. But while touchplates typically apply additional color to a portion of an image, it’s also possible to apply colors across the entire image—to print in six or more colors.

Adding extra colors—or different tones of the four process colors—to CMYK inks can help capture a wider slice of the spectrum of colors visible to the eye and allow designers to create special effects and match custom colors. Depending on the two additional colors that are chosen, six-color printing can be especially useful in reproducing oranges, greens and purples, which are difficult to create by combining two of the subtractive primaries. Six-color may not be as valuable when it comes to blues, which can be reproduced well using the four process colors. However, even blues could be pumped up by using special, high intensity inks or adding an additional blue to the traditional CMYK inks.

Some printers use a complete six-color process printing system. In 1995, Pantone Inc. introduced Hexachrome^® six-color process printing, which uses specially modified versions of CMYK inks along with orange and green. The system promises to reproduce more than 90% of all of the Pantone Matching System colors, almost twice the number that can be captured using conventional four-color process printing.

The Hexachrome system is most widely used by packaging printers, who value its ability to faithfully reproduce a wide variety of the colors without ever having to resort to spot colors or change the inks on the press. Once the press is equipped with Hexachrome inks, the press can print a wide variety of projects, in a wide range of colors, with fewer printing plates, less make-ready and wash-up time and no second passes through the press.

People familiar with the system say it can offer other advantages compared to conventional four-color too, including more accurate pastels and outstanding skin tones. Images with dark details and full rich colors, such as dark leather, deep wine, walnut, mahogany and other dark woods may also be good candidates for six-color printing. And high-purity Hexachrome inks are so vivid that that some printers are using them in place of standard process inks to print four-color images with greater opacity and intensity.

But six-color printing is not for every project. Even though the projects can be printed in a single pass through the press, there is still the time and expense of preparing additional plates. The premium inks that often are required are more expensive too. And while six-color process printing can deliver more colors than conventional four-color printing, it cannot duplicate all of the special effects that are possible with two touchplates.

Those are not the biggest drawbacks, however. The greatest hurdle to six-color printing is the need for specialized separating and proofing systems and techniques. Because six-color printing has a greater range of color than conventional CMYK printing, six-color images must be prepared using color monitors and the additive primary colors.

Any object that radiates light (as opposed to reflecting light, like paper) emits light in the three additive primaries of red (R), green (G), and blue (B). By mixing, or adding, any of these two colors,—in overlapping beams of light on a conventional video screen, for example—the intermediate colors are reproduced. White is formed by combining all three additive primaries, while black is their total absence.

The RGB color space is much larger than the CMYK color space—it contains more colors. But almost all images created, stored or processed using RGB colors must be converted into CMYK inks in order to be printed on paper. And that’s where the trouble begins. The translation from RGB to CMYK is never perfect. Not all of the colors seen on the monitor can be printed, and not all printed colors can be accurately matched on a monitor. So what you see on the monitor is likely to be different than what you see on the proof, or on the press.

Six-color presses—and six-color printing—offer designers and printers new options. But no matter how many colors you use, the paper you choose will have an enormous impact on the way the printed colors look.

As we said earlier, printing “works” by bouncing light off the paper through the colored films of transparent inks to produce the colors seen by the eye. So the brighter the surface, the brighter the color, and the whiter the surface, the wider the range of the colors we see.

The brightness of paper is controlled by how the pulp is bleached, the mixture of dyes and pigments it uses and often, by the addition of special brightening agents. Depending on the standard of measurement, higher quality white coated papers have brightness ratings in the 80s and 90s, even all the way to 100%, with the numbers reflecting the percentage of light striking the surface of the paper that is reflected back to the eye.

While brightness determines the intensity of the colors we see, whiteness determines the range of the colors that we see. A paper that is white reflects all colors equally and comes the closest to reproducing the full spectrum of visible light. However, many papers have a slight blue tint. The reason is that due to the physiology of the human eye, a little bit of blue heightens the perception of brightness and whiteness. The trick is not to overdo it, since the tint begins to act as a filter and change the colors reflected to the eye. The rule of thumb is that if you can detect a strong impression of color—blue or any other—in a plain sheet of paper, the shade is likely to affect the accuracy of the color reproduction. Your best bet is to choose a paper whose shade complements the subject—or a subtle shade that that won’t distort the final results.

But there’s more to paper than brightness and whiteness. The surface of the paper is equally important. Just as a still mountain lake reflects a sharper image than one that is broken by ripples, the smoother the surface of the paper, the crisper the image will be. That’s because rougher surfaces tend to scatter the reflected light, reducing the clarity of the image and distorting the subtleties of its tones.

Ink holdout—the paper’s ability to keep a thin, uniform film of ink on the surface of the paper—is another key factor in capturing color. If the ink is allowed to spread into the paper’s pores and capillaries, the printed dots lose their definition, which results in reduced color contrast and uneven color density.

So for the best color reproduction, you need a smooth, bright, white surface and outstanding ink holdout. And the best place to find them is in premium coated papers such as the gloss, dull and matte papers showcased in this website. That’s because the hard surface of coated paper holds inks, varnishes and other finishes on the top of the paper, without allowing it to run into the valleys found in the surface of uncoated stocks. The smoother the finish, the better the quality of the color. Simple.