A Detailed Analysis of Color Printing Design Standards

Release date:

2019-06-24 15:37

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According to the ink density ranges specified in the guidelines, any ink overprint sequence—YMC, YCM, CMY, CYM, MCY, or MYC—can be used. However, does each sequence produce the same color in print design? In fact, it does not.

Even when the in‑field density is controlled at a fixed absolute value, each overprint sequence in print design will yield distinct red, green, and blue overprint colors, because the ink formulations used in each printing process possess unique properties—such as ink opacity, which affects coverage. Consequently, the surface energy of the dried ink film from the earlier print pass can influence the adhesion characteristics of the wet ink applied in the subsequent pass.

In print design, the three primary ink colors are mixed in varying proportions to produce the desired spectral hue values. The accuracy and balance of the densities of these three primary inks on the substrate are directly attributable to the print designer. Although printing operators can only measure and adjust ink densities within a limited range, these density specifications enable designers to achieve a broad spectrum of overprinted ink colors—whether the inks are transparent or the substrate is pure white. In print design, these density ranges can be readily found in various relevant standards, such as those outlined in the FIRST and SWOP guidelines.

Yellow pigment has poor opacity, while magenta and cyan pigments exhibit good opacity. However, yellow pigment inks possess high surface energy.

The first step in color management for print design is to determine the optimal ink-overprint sequence and a density balance that delivers a wide color gamut.

The GATF Association developed a simple hexagonal color chart many years ago to visualize the relationships among different colors. A densitometer can assess color quality by measuring hue deviation, gray balance, and overprint density, and it can be compared with the three primary colors.

For example, in a hexagonal color diagram, the three non‑adjacent vertices represent the ideal ink primaries (YMC), while the other three vertices correspond to overprinted composite colors (RGB); the center of the hexagon denotes neutral tones, ranging from white through gray to black. The greater the ink density, the closer the color lies to one of the vertices and the farther it is from the neutral axis.

When the process colors and composite colors of an actual print design are mapped onto a hexagonal color chart, the densities, color differences, and gray levels of the three primary inks (CMY) and the composite colors (RGB) are revealed.

Because the ink is not entirely ideal, the hexagonal (irregular) distribution will not match the size of a perfect hexagonal color chart; however, it can still be used for optimized printing. Therefore, by employing the GAFT method to generate an irregular hexagonal distribution that conveys information on the three primary colors and composite colors in a print design, one can achieve optimal density and the most effective overprint sequence.

The size of the color‑coverage area determines the overall ink’s color‑rendering performance and the contrast intensity of the printed design; naturally, a larger area is preferable.

Other density values can also be incorporated into the printing‑design measurement sequence, such as 25%, 50%, and 75% dot densities.

If the distribution of these other tone values is concentrated, it indicates that the print design is under control; conversely, if the distribution is dispersed, it suggests that the print design has gone out of control and requires appropriate adjustments.

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