Color constancy
A white shirt looks white under orange lamplight and in blue shade. Your brain quietly subtracts the light.
- The dress
- February 2015
- Saw blue/black
- 57% (Lafer-Sousa et al. 2015)
- Retinex theory
- Edwin Land, 1970s
Color constancy is the brain's habit of seeing an object's color rather than the light coming off it. A white page under a warm bulb sends yellowish light to your eye, and the same page in blue shade sends bluish light, yet you see white both times. The brain estimates the lighting and discounts it, much as it judges a color against its neighbors in simultaneous contrast.
In February 2015 a photo of a striped dress split the internet. Some saw white and gold; others saw blue and black (the real dress was blue and black). In a study of over 1,400 people, Rosa Lafer-Sousa and colleagues found 57% saw blue/black and 30% white/gold. The photo hides its lighting, so each brain guessed. Assume cool shade and you subtract blue and see white-gold. Assume warm light and you see blue-black.
Edwin Land, the inventor of Polaroid instant photography, made constancy famous in the 1970s with 'Mondrian' displays: patchworks of colored paper lit by three adjustable projectors, roughly one for each cone type. A patch kept its color even when the light it sent to the eye changed a lot, because the brain compares each patch with the rest of the scene, the same principle Josef Albers taught with paper squares. He called his theory retinex, from retina plus cortex.
Constancy keeps you alive and trips up painters. Beginners paint snow white because they know it's white; Monet painted it in blues and lilacs because that's the light he saw. His Rouen Cathedral series shows one stone facade changing color with the hour. See also simultaneous contrast.
Swatches
- Photo pixels · pale blue
- Photo pixels · brown-gold
- Real dress · blue
- Real dress · black
Colors
Sources
- Lafer-Sousa, R., Hermann, K. L. & Conway, B. R. (2015). Striking individual differences in color perception uncovered by 'the dress' photograph. Current Biology 25(13): R545–R546.
- Land, E. H. (1977). The retinex theory of color vision. Scientific American 237(6).
- Foster, D. H. (2011). Color constancy. Vision Research 51(7): 674–700.
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