# Brightness perception

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Brightness is an attribute of visual perception in which a source appears to emit a given amount of 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.

## TerminologyEdit

"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.[1]

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

In the RGB color space, brightness can be thought of as the arithmetic mean μ of the Red, Green, and Blue color coordinates[How to reference and link to summary or text] (although some of the three components make the light seem brighter than others, which, again, may be compensated by some display systems automatically):

$\mu = {R + G + B \over 3 }.$

Brightness is also a color coordinate in the HSB or HSV color space (hue, saturation, and brightness or value).

## Brightness of soundsEdit

The term "brightness" is also used in discussions of sound timbres, in a rough analogy with visual brightness. Timbre researchers consider brightness to be one of the perceptually strongest distinctions between sounds[2], and formalize it acoustically as an indication of the amount of high-frequency content in a sound, using a measure such as the spectral centroid.