Luminous Power Per Unit Area for Source
(Luminous Exitance)

Luminous Exitance applies to the light emitted by a luminous source. Luminous exitance is a measure the total amount of light leaving a point on a surface into all directions outside the surface. For all emitted electromagnetic radiation, the corresponding term would be radiant exitance. The luminous exitance is the radiant exitance factored by the response curve of the human eye. The SI unit for luminous exitance is lumens per square meter (lm/m²).