retinex theory

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A theory of colour vision according to which the visual system includes three separate eye-brain systems called retinexes, each with a peak sensitivity to long-wave light (560 nanometres), medium-wave light (530  nm), or short-wave light (430  nm) and inhibitory effects on the other systems, operating to assign a colour to each spot in the visual field according to the ratio, for each of the three retinexes, of light reflected from that spot to the average of the light reflected from its surround, the resulting triplet of ratios uniquely defining the colour at each spot. The theory, which was put forward by the US physicist Edwin H(erbert) Land (1909–91), inventor of the Polaroid Land camera and president of the Polaroid Corporation, in the Journal of the Optical Society of America in 1971, accounts for the Land effect and for colour constancy, because relative rather than absolute wavelengths determine perceived colour, the perceived colour of an object remaining constant as long as the reflectance ratios are unchanged, even if the total amount of light of any given wavelength varies markedly, and this explains why colour constancy is disrupted and some colours cannot be perceived at all when surfaces are viewed in void mode. [Coined by its inventor from retin(a) + (cort)ex]

Subjects: Psychology.

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