Related Experiment Video
Updated: Oct 17, 2026

Visualizing Visual Adaptation
Published on: April 24, 2017
Relational color constancy in achromatic and isoluminant images
1Departamento de Física, Universidade do Minho, Braga, Portugal. smcn@fisica.uminho.pt
Abstract:
Relational color constancy, which refers to the constancy of perceived relations between surface colors under changes in illuminant, may be based on the computation of spatial ratios of cone excitations. As this activity need occur only within rather than between cone pathways, relational color constancy might be assumed to be based on relative luminance processing. This hypothesis was tested in a psychophysical experiment in which observers viewed simulated images of Mondrian patterns undergoing colorimetric changes that could be attributed either to an illuminant change or to a nonilluminant change; the images were isoluminant, achromatic, or unmodified. Observers reliably discriminated the two types of changes in all three conditions, implying that relational color constancy is not based on luminance cues alone. A computer simulation showed that in these isoluminant and achromatic images spatial ratios of cone excitations and of combinations of cone excitations were almost invariant under illuminant changes and that discrimination performance could be predicted from deviations in these ratios.
Related Concept Videos
Perceptual Constancy
Size constancy is the recognition that an object remains the same size, even when its image on the retina changes. For instance, a bus is perceived to be large enough to carry people, even if it looks tiny from...
Color Vision
Photoreceptors and Visual Pathways
Anatomy of the Eyeball
Gestalt Principles of Perception
Vision

