Darkness, the polar opposite to brightness, is understood to be an absence of visible light. It is also the appearance of black in a colored space.
Humans are unable to distinguish color when either light or darkness predominate. In conditions of insufficient light, perception is achromatic and ultimately, black.
The emotional response to darkness has generated metaphorical usages of the term in many cultures.
The perception of darkness differs from the mere absence of light due to the effects of after images on perception. In perceiving, the eye is active, and that part of the retina that is unstimulated produces a complementary afterimage. Read more