Emission theory (vision)

For Newton's proposal that light is emitted from luminous objects in the form of particles or corpuscles, see Emission theory (relativity).
Illustration from System der visuellen Wahrnehmung beim Menschen (1687) depicting emission theory.

Emission theory or extramission theory (variants: extromission) or extromissionism is the proposal that visual perception is accomplished by eye beams emitted by the eyes. This theory has been replaced by intromission theory (or intromissionism), which is that visual perception comes from something representative of the object (later established to be rays of light reflected from it) entering the eyes. Modern physics has confirmed that light is physically transmitted by photons from a light source, such as the sun, to visible objects, and finishing with the detector, such as a human eye or camera.