Achieving consistent colours in digital printing

Abstract: The characterization of the transfer function of a printing device is a complex procedure involving not only the device itself but also the paper and its properties. In digital printing, the complexity is increased by the lack of standardisation and guidelines. The work reported here is an an important step in the development of a library of characterization procedures. These procedures can be applied to printing situations with different combinations of printing engines and paper grades. An example of a building block is colour separation with respect to halftoning techniques and available inks or toners. Another is the characterization of the physical properties of the paper substrate. The most common characterization procedure is through the ICC-pro file. Device ICC-profiles contain the data needed for a colour management system (CMS) to do colour separation and colour mapping. In this study special emphasis was put on the influence of the paper properties and on how they affect the profile. Glass, surface roughness, whiteness and light scattering are all measurable paper properties that will affect colour reproduction. Ink and paper interaction and especially ink penetration are also phenomena that affect colour reproduction and thus the ICC profile. Presently, there are no direct links between paper quality parameters, like the CIE whiteness level, and quality of colour reproduction.