The retinex of colour vision impairment

Abstract

AbstractThe concept of the “Retinex” was introduced by Edwin Land in 1962. The aim of his theory of colour vision was to highlight the observations on colour perception that were at odds with the simple “Newtonian” concept that the colours that humans perceive when viewing narrow band light are directly related to perceived colours in the environment. There are, however, two particular observations which are at odds with this simple interpretation of the colours seen in the “spectrum” of light. One was emphasized by Gӧethe in his colour theory: namely that there are a range of named colours that are influenced by the luminance contrast (e.g. brown which is a darkened orange) or closeness of the colour to white. This was explored by Chevreul, Munsell and others who developed systems of colour based on the three dimensions: hue (colour category), saturation (closeness to white) and value (brightness). The second was the observation studied extensively by Land: namely that colours remain constant across a certain range despite a change in the spectral content of the illuminant. Thus despite a change in the pattern of cone excitation the colour appearance does not change. Land also emphasized that this phenomenon is influenced by other colours in the scene and introduced the study of natural scenes with natural illumination rather than narrow band light in the laboratory.So in this context Land decided to refer to the “Retinex” as it was clear that the various processes were taking place both at the retinal and cortical levels. I am adopting this term in my talk because clinical studies provide an opportunity to study the influence of damage at all levels in the visual pathway on colour perception. Beginning with congenital colour anomalies affecting the cone opsins all the way to damage to extra‐striate visual cortex clinical studies, such as those presented in this symposium, alterations in colour vision provide an insight into how damage at various levels in the “Retinex” influence colour perception.