Characterization of Multicolor Printing: Challenges and Solutions

Hanno Hoffstadt, GMG GmbH & Co. KG

Color management includes the steps process calibration, color separation, and color conversions, with the help of profiles. But everything starts with print character- ization – measuring the color of overprinted ink combinations -, from which calibra- tion aims, and ultimately standards, can be developed. For multicolor printing beyond CMYK, a reliable characterization of the color of overprints is still a challenge in gen- eral.

This paper revisits the familiar history of CMYK test charts and the (supposed) reasoning behind them, and explores the extension to more than 4 inks. The com- binatorics immediately lead to impractically high numbers of patches (see example figures at end). These are contrasted with the available printing space and constraints of printing processes and measurement devices. A full characterization of all those ever-changing multicolor combinations that occur in day-to-day packaging production is therefore usually avoided. This makes overprints with arbitrary spot colors difficult to predict, so that they are often simply not used in the design.