Rules for colour constancy.

Abstract

Colours of objects tend to be constant regardless of the colour of the illuminant, therefore, regardless of the quanta catch of the retinal cones. Various mechanisms for this including context recognition, adaptation of retinal sensitivities and independent processing by receptor types have been proposed. These present experiments test the hypothesis that colours are determined by the normalized relationship between all colours in the field of view. In this hypothesis, colours are constant in classical experiments simply because changes of the illuminant do not disrupt the relationship between quanta catches across the field of view. The experiments consist of making sets of colour displays; each with the same relative quanta catches, but different absolute reflectances. 'Colour tautomi' arrays of five colour patches were printed using controlled amounts of yellow, magenta, cyan and black toners. The experiment began with a control 'colour tautomi' array of reflectances with measured relative quanta catches. New arrays of colours were then chosen that increased (or decreased) the reflectances, and quanta catches, a constant amount for the entire array. These changes were done independently for each receptor type. When these 'colour tautomi' are viewed in the room, each array has a different set of colours. When viewed in a restricted field of view, all arrays appear the same. In a further experiment new areas such as white are added to the display. Colour constancy is a field phenomenon controlled by the relative quanta catches in the field of view. Absolute colour constancy is controlled by the relative quanta catches in the field of view and the absolute quantum catches of the receptors.