Evidence is presented that colar constancy does not exist as a special phenomenon of human color vision. It is argued that results of experiments, as well as casual observations, which seem to illustrate color constancy, can be easily understood from basic facts about chromatic adaptation and simultaneous contrast. The argument is supported by (i) a critique of the famous Mondrian studies, (ii) the ATD model's predictions of the Mondrian data, and (iii) a summary of a demonstration experiment regarding Mondrian patterns. Concerning definitions of color concepts, it is noted that, in any field of science, definitions change according to theoretical advances, but the vocabulary of color vision has not. In particular, the ATD models of the past ten years or so suggest that some of the universally accepted and seemingly essential terms of color require re-examination.
This paper reviews and critiques earlier version of the ATD model, and it describes a revised model, which differs mainly in its gain control function. The model is applied to recently published lightness, hue and colorfulness data.
Using a slightly modified version of an earlier model, and using a new rule for simulating the effects of simultaneous or successive chromatic adaptation, excellent predictions are made for experimental data that offer especially strong challenges to models for chromatic adaptation.
An historical background is provided for the ATD model for color perception and visual adaptation, whose developing variations have appeared over a period of several years, and which is applied to several sets of chromatic adaptation data in the succeeding companion paper.
Proc. SPIE. 1913, Human Vision, Visual Processing, and Digital Display IV
KEYWORDS: Visual process modeling, Data modeling, Visualization, Signal attenuation, Interference (communication), Colorimetry, Color difference, Human vision and color perception, Receptors, Eye models
An improved version of an earlier unified model for human color perception and visual adaptation is described. It allows superior predictions of color discriminations and color appearances under varying adaptation conditions. Accordingly, the model provides not only color equations for small-step and large-step color differences, but also equations for predicting many other visual responses including actual perceptions of hue, saturation, and brightness.