Traditional inkjet printers use cyan, magenta, yellow and black (CMYK) inks to produce all the colours that we can print, but they cannot perform spectral printing (reproduction of lighting effects). Using more than four inks will allow for spectral printing, but this advancement needs to be tested stringently before it can be used. The EU-funded CP7.0 (Colour printing 7.0: Next generation multi-channel printing) project advanced colour printing technology by studying the spectral properties of 7-colour printing. CP7.0 also provided much-needed skills development in the field of printing technology research. To achieve its aims, the project reviewed the current state of multichannel spectral printers, focusing on halftones and spectral reproduction workflows. Its research allowed scientists to choose software that could be used in a spectral printer design, called spectral models. A spectral model that includes fluorescence was also developed. A method to relate actual image quality to modelled images for halftone printing was created as well. In parallel, researchers looked at ways to adapt current halftone algorithms to 7-channel printing. Investigating how multichannel printing could be used for fine art printing, CP7.0 developed a new ink mixing process that can help create new colours. Researchers also explored so-called 2.5D printing, which uses multiple layers of ink to produce a textured surface. Importantly, the project provided training workshops and conference events to promote skills development in this field. Excellent research emerged from the project in four key areas. It made headway in spectral modelling of the printer/paper/ink combination, as well as on spectral gamut prediction and gamut mapping. The effect of paper optical and surface properties on the colour reproduction of multichannel devices was also successfully researched. The fourth key area looked at optimal halftoning algorithms and tonal reproduction characteristics of multichannel printing. Together with the experimental work, these achievements represent a large step towards the next generation of inkjet printing.
Multichannel inkjet printer, spectral printing, CMYK, CP7.0, colour printing, halftone