Unsolved Problems of Color Reproduction.

Colorimetry is an essential pillar of modern methods of color reproduction (e.g. masking methods, electronic color correctors). Although colorimetric research has been pushed to extreme accuracies, in several fields a number of problems that are of basic importance to color reproduction have hardly ever been investigated. Such problems are, for instance, the effects of change of illumination, size of reproduction, frame or other surrounding, and contrast. The few existing investigations will be reported. Methods suitable for such investigations will be outlined. The results cannot be expected to be as accurate as those of the existing colorimetry, but, they are as accurate as required for practical applications. Photographic processes are superior to methods using a time sequential transmission of picture elements (TV or electronic color correctors) insofar as the latter methods have to be designed for a much greater accuracy than required by the observer's eye.