{{Short description|Perception of light level}} {{Other uses}} thumb|Decreasing brightness with depth (underwater photo as example)
'''Brightness''' is an attribute of visual perception in which a source appears to be radiating/reflecting light.<ref>"[http://www.merriam-webster.com/dictionary/bright Bright Definition & Meaning]", Merriam-Webster Dictionary.</ref> In other words, brightness is the perception dictated by the luminance of a visual target. The perception is not linear to luminance, and relies on the context of the viewing environment (for example, see White's illusion).
Brightness is a subjective sensation of an object being observed and one of the color appearance parameters of many color appearance models, typically denoted as <math>Q</math>. Brightness refers to how much light ''appears to shine'' from something. This is a different perception than lightness, which is how light something appears ''compared to'' a similarly lit white object.<ref>Robert William Gainer Hunt: ''Some comments on using the CIECAM97s colour-appearance model''</ref>
The adjective ''bright'' derives from an Old English ''beorht'' with the same meaning via metathesis giving Middle English ''briht''. The word is from a Proto-Germanic {{lang|gem-x-proto|berhtaz}}, ultimately from a PIE root with a closely related meaning, {{lang|ine-x-proto|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.<ref>“[http://www.its.bldrdoc.gov/fs-1037/dir-005/_0719.htm Brightness]” in Federal Standard 1037C, the ''Federal Glossary of Telecommunication Terms'' (1996)</ref> Brightness is an antonym of "dimness" or "dullness".
With regard to stars, brightness is quantified as apparent magnitude and absolute magnitude.
Two pictograms resembling the Sun with rays are used to represent the settings of luminance in display devices. They have been encoded in Unicode since version 6.0 (October 2010) in the Miscellaneous Symbols and Pictographs block under U+1F505 as "low brightness symbol" (🔅) and U+1F506 as "high brightness symbol" (🔆).<ref>{{cite web |url=https://unicode.org/charts/PDF/U1F300.pdf |title=Miscellaneous Symbols and Pictographs |publisher=Unicode Consortium |year=2023}}</ref>
The United States Federal Trade Commission (FTC) has assigned an unconventional meaning to ''brightness'' when applied to lamps: on light bulb packages, ''brightness'' means luminous flux, while in other contexts it means luminance.<ref name="ftc">{{cite web |title=Shopping for Light Bulbs |publisher=United States Federal Trade Commission |url=https://www.consumer.ftc.gov/articles/0164-shopping-light-bulbs |access-date=March 13, 2017}}</ref> Luminous flux is the total amount of light coming from a source while luminance is the amount of light per unit solid angle per unit of area on the source's surface. The table below shows the standard ways of indicating the amount of light.
{{SI light units}}
==See also== * Luma (video) * Luminance (relative) * Luminosity
==References== {{Reflist}}
==External links== {{Commons category-inline|Brightness|lcfirst=yes}} {{wiktionary|brightness}} * [http://www.poynton.com/ColorFAQ.html Poynton's Color FAQ]
{{Authority control}}
Category:Vision Category:Photometry