Since 0. Lummer [6] and the industrial development and production of artificial illuminants it became more and more evident that between sunlight and human vision a specific until today unexplained - “resonance” condition apparently exists. Therefore the recommendation holds to approximate as much as possible the spectral energy distribution of artificial illuminants to the one of sunlight. Especially in human color vision spectral shifts of illuminants always lead to hue shifts (combined 13rightness-, Hue-, Saturation-Shifts) in the perception of colors. These hue shifts in human vision adaptively become compensated with more or less time delay, leading to a relatively good “color constancy” under variable illuminants. An always far from perfect - explanation model, the von Kries-model, attributes this adaptive compensation of hue shifts to the photopigments in the cones of the human retina. Other - less perfect - models attributing this adaptation to cortical functions also exist [1, 2]. In parallel the need becomes evident to realize future color sensors “capable to measure colors normalized to the spectral sensitivity curves of human vision” [7]. It might be registered with satisfaction that a growing objectivity comes into this psychophysical field of color constancy in human vision by the publication of more and more precise data on relevant parameters in the physical conditions of the experiments.
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