Perceptual Constancies: Brightness Constancy

Brightness constancy (also known as lightness constancy) allows humans to identify an object as having a constant color even if the light in the environment changes. That is, no matter the level of the light, we can still tell the color of an object.

For example, due to brightness constancy, humans can tell that snow is white even in the darkest of places. Also, they can tell that coal is black even under bright sunlight. Even though the illumination in both environments is very different, humans are able to differentiate the color of the objects, and that color is constant no matter how much sunlight there is.