Colour constancy

What is colour constancy? Colour constancy is the tendency of objects to appear the same colour even under changing illumination. A yellow banana appears yellow whether you see it in the tungsten light of the kitchen or in sunlight outdoors. Under these different conditions, the banana reflects very different light spectra to your eyes, but you see instead its unchanging material properties. That is, you see that the banana tends to reflect more light in the ‘yellowish’ region of the spectrum compared with other objects, regardless of the spectrum of light shining on all of them, and you conclude that the banana is inherently ‘yellow’. Colour constancy is not a property of objects; it is a perceptual phenomenon, the result of mechanisms in the eye and brain.