Digital Offset Printing – Going Beyond 4 Colors

Abstract

While 4-color CMYK printing is the norm for mainstream offset printing, all HP Indigo digital presses have the option of printing with up to 5, 6 or 7 different colors. These extra color stations can be used to improve image quality by increasing the color gamut, decreasing graininess, reducing illumination sensitivity, or adding special effects to the printed output. The HP IndiChrome Pantone® certified ink mixing system is one key enabler of these improvements, allowing customers to create Pantone® or custom-matched spot colors at their own site.In this paper, we show how the color gamut of a digital press can be increased through the use of additional full-density inks, such as green and violet. We also show how the graininess of a print can be decreased through the use of light inks. In particular, we show how the addition of a gray ink can decrease the illumination sensitivity, improve the gray neutrality, and reduce the graininess of a print. Finally, we highlight some of the special effects that can be created when using specialty inks such as the digital matte ink.