Spectral Colour Reproduction

Collaborators:

Gjøvik University College,
École Nationale Supérieure des Télécommunications, France.
Project leader:
Dr. Jon Y. Hardeberg
Project co-ordinator:
Francis Schmitt
PhD student:
Mr. Jérémie Gerhardt

Project Outline

We suggest that it is possible to reproduce multispectral colour images faithfully on printed media, using a multi-channel image reproduction system. The goal is to reproduce images with a spectral match to an original scene, or a reference image, in order to eliminate the problems of the conventional metameric matches that can be achieved with four-color printing processes. A metameric match is only correct under a given viewing illuminant, while a spectral match is correct under any illuminant.

Spectral modelling of different printers, and development of halftoning algorithms suitable for multi-colorant printing, are two topics, which, in addition to their importance for multispectral reproduction, also can be interesting for conventional colour printing. The question of how many channels that are needed is relevant for both acquisition and reproduction. Related to this question is the question of how to evaluate the quality of a multispectral colour image.

This spectral match can only be achieved through careful selection of colorants and an innovative separation algorithm. One possible strategy for this would be to first make a colorimetric match through conventional four-color separation techniques, and then add the extra channels in order to reduce metamerism. Another strategy is to use spectral printer models for the separation, for example the Yule-Nielsen modified spectral Neugebauer equations.

The research is funded by : The Research Council of Norway

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