Incomplete Chromatic Adaptation under Mixed Illuminations

摘要

A set of psychophysical experiments was conducted to investigate the state of adaptation between hardcopy and softcopy images when viewed under mixed illuminations. The experimental procedures closely followed the guidelines of the CIE Technical Committee TC8-04 Adaptation under Mixed Illumination Conditions. Three chromatic adaptation transforms (CMCCAT97, CMCCAT2000 and CIECAT94) and the S-LMS mixed adaptation model were evaluated. Each chromatic adaptation transform includes an adaptation ratio. This experiment was intended to find the best ratio for each model. Paired comparison technique was used to determine the degree of colour match between the print originals and softcopy reproductions viewed under different illuminants (or white points). The simultaneous binocular matching method was employed. The experiment was divided into nine phases in accordance with a change of illuminants and luminance levels of the ambient light. Fifteen observers took part in each experimental phase. The results reveal that the state of adaptation of human visual system is about 40-60%, and this is independent of illumination conditions. Reliable CATs with a proper incomplete adaptation ratio are capable of producing appearance colour matches under mixed adaptation. Overall results show that CMCCAT2000 and CMCCAT97 gave better performance than CIECAT94 and S-LMS mixed adaptation model.