Color Gamut Extension on 4-color Sheet-fed Offset Press Using Ink Fountain Divider Methodology


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Dr. Ruoxi Ma and Brian Lawler


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The purpose of this study is to investigate a new way to utilize a wide format 4-color offset press to print a wider color gamut. Printing with 7 color creates a wider color gamut with more vivid area and more depth in color. This methodology could be used on the Heidelberg SM CD74 or any other wide format 4 color offset press to output 4+ color job with less trimming waste and wider color gamut.

In this study, a test chart was created with i1 Profiler. The test chart was printed on Heidelberg SpeedMaster CD 74 on glossy coated paper. The press was setup with 2 color inks on the second, third and fourth unit by using an ink divider in the middle of each ink fountain tray. The C, M, Y, K, Pantone Orange, Violet and Green will be printed with 2 passes on the same side of substrate, flipped from left to right, bottom to up.

This method of printing will lead to huge enhancement in the measured color gamut, which in this case provided by the KCVMOGY (Black-Cyan-Violet-Magenta-Orange-Green-Yellow) inks. However, this print method will also reduce the width capacity of the substrate on this press to half of its current capacity. For example, the biggest substrate width of Heidelberg CD 74 is 74cm, with the 7-color setting, the biggest substrate width will be 37cm instead.

The printed results will be characterized by measuring the CIELAB values and the reflectance spectra with an X-Rite i1iO spectrophotometer with 45deg/0deg geometry. Profile Maker will be used to make the ICC profiles for the ink and substrate combinations. Color volumes will be created by ColorThink Pro. The KCMY color gamut and KCVMOGY color gamut will be compared accordingly.

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