Darkness

Darkness, the direct opposite of luminosity, is defined as a lack of illumination, the absence of visible light, or a surface that absorbs light, such as black or brown.

Human vision cannot distinguish colors in very low lighting conditions. Color sensitive photoreceptor cells in the retina are inactive when light levels are insufficient, in the range of visual perception known as scotopic vision.

The emotional response to darkness has resulted in the metaphorical use of the term in various cultures, usually used to describe feelings of unhappiness or foreboding.

Referring to the time of day, total darkness occurs when the Sun is more than 18° below the horizon, without the effect of twilight on the night sky.

From a physical point of view, an object is said to be dark if it absorbs photons so that it appears fainter than other objects. For example, matte black paint reflects less visible light and appears dark, whereas white paint reflects a lot of light and appears bright.[1] An object may appear dark, but may actually be bright at a frequency that humans cannot see.