Brightness Constancy

Visual objects appear constant to us not only in their shape and size, but also in their degree of whiteness, greyness, or blackness, even though the actual amount of physical light energy reflected from them may change quite considerably. In other words, our experience of an object's brightness does not shift in step with genuine changes in the amount of light actually being reflected toward our eyes. The tendency to perceive an object's apparent brightness as staying constant under different levels of illumination is called brightness constancy. For example, the surface of a sheet of paper that appears white in bright sunlight continues to be perceived as white when seen indoors in ordinary room light; simi …