Brightness

{{Short description|Perception of light level}}

{{Other uses}}

File:LightningVolt Deep Blue Sea.jpg

Brightness is an attribute of visual perception in which a source appears to be radiating/reflecting light."[http://www.merriam-webster.com/dictionary/bright Bright Definition & Meaning]", Merriam-Webster Dictionary. 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 $Q$. 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.Robert William Gainer Hunt: Some comments on using the CIECAM97s colour-appearance model

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, *{{PIE|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.“[http://www.its.bldrdoc.gov/fs-1037/dir-005/_0719.htm Brightness]” in Federal Standard 1037C, the Federal Glossary of Telecommunication Terms (1996)

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+1505 as "low brightness symbol" (🔅) and U+1F506 as "high brightness symbol" (🔆).{{cite web |url=https://unicode.org/charts/PDF/U1F300.pdf |title=Miscellaneous Symbols and Pictographs |publisher=Unicode Consortium |year=2023}}

The United States Federal Trade Commission (FTC) has assigned an unconventional meaning to brightness when applied to lamps. When appearing on light bulb packages, brightness means luminous flux, while in other contexts it means luminance.{{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}} Luminous flux is the total amount of light coming from a source, such as a lighting device. Luminance, the original meaning of brightness, is the amount of light per solid angle coming from an area, such as the sky. The table below shows the standard ways of indicating the amount of light.

{{SI light units}}