Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. This is a subjective attribute/property of an object being observed.

The adjective bright derives from an Old English beorht with the same meaning via metathesis giving Middle English briht. The word is from a Common Germanic *berhtaz, ultimately from a PIE root with a closely related meaning, *bhereg- "white, bright".

"Brightness" was formerly used as a synonym for the photometric term luminance and (incorrectly) for the radiometric term radiance. As defined by the US Federal Glossary of Telecommunication Terms (FS-1037C), "brightness" should now be used only for non-quantitative references to physiological sensations and perceptions of light.

A given target luminance can elicit different perceptions of brightness in different contexts; see, for example, White's illusion.

In the RGB color space, brightness can be thought of as the arithmetic mean μ of the red, green, and blue color coordinates (although some of the three components make the light seem brighter than others, which, again, may be compensated by some display systems automatically):

Matt Richards (born 21 November 1967) is a television producer/director/writer from St Minver in Cornwall.

After attending the University of Westminster Film School he raised the budget to follow explorer Michael Turner on an expedition to Senegal and the Cape Verde Islands and make a short film about his efforts to document the landing places of Sir Francis Drake. This film was so well received that the BBC commissioned him to complete the film which included a voyage to Panama to attempt to locate and raise the coffin of Sir Francis Drake. This expedition failed but the subsequent film In Drake's Wake was shown on BBC2. His next film was The Gold Plane, again for BBC2. Narrated by John Nettles, this 50-minute film followed the quest to prove that a plane crash in 1944 was the work of sabotage to prevent the secrets of D-Day being revealed to General Charles de Gaulle in Algiers. Since then he has made several historical documentaries which include Spilt Blood, In Search of the King, The Falklands War - The Real Thing, People's War, Industrial Revelations - Best of British and Secrets Beneath Our Feet.