The candela per square metre (symbol: cd/m
2) is the unit of
luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls with ...
in the
International System of Units
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
(SI). The unit is based on the
candela
The candela ( or ; symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous t ...
, the SI unit of
luminous intensity, and the
square metre
The square metre ( international spelling as used by the International Bureau of Weights and Measures) or square meter (American spelling) is the unit of area in the International System of Units (SI) with symbol m2. It is the area of a square ...
, the SI unit of
area
Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an op ...
. The nit (symbol: nt) is a non-SI name also used for this unit (1 nt = 1 cd/m
2). The term ''nit'' is believed to come from the Latin word , "to shine".
As a measure of light emitted per unit area, this unit is frequently used to specify the brightness of a display device. The
sRGB
sRGB is a standard RGB (red, green, blue) color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the International Electrotechnical Commission ...
spec for monitors targets . Typically, monitors calibrated for
SDR broadcast or studio color grading should have a brightness of . Most consumer desktop
liquid crystal display
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but ...
s have luminances of 200 to 300 cd/m
2.
HDR displays range from 450 to above 1600 cd/m
2.
Comparison with other units of luminance
One candela per square metre is equal to:
*10
−4 stilbs (the
CGS unit of luminance)
*π×10
−4 lamberts
*π
apostilbs
*0.292
foot-lamberts
*π×10
3 skots
*π×10
7 bril
Bril is a surname. Notable people with the surname include:
* Ben Bril, Dutch boxer
*Joel Bril, pen name of Joel Löwe
* Matthaeus Bril, Flemish painter
*Paul Bril
Paul Bril (1554 – 7 October 1626) was a Flemish painter and printmaker princi ...
s
*1 nit
See also
*
Orders of magnitude (luminance)
*
Photometry (optics)
Photometry is the science of the measurement of light, in terms of its perceived brightness to the human eye. It is distinct from radiometry, which is the science of measurement of radiant energy (including light) in terms of absolute power. ...
References
{{reflist , 64em
External links
IEC 61966-2-1:1999 Multimedia systems and equipment – Colour measurement and management – Part 2-1: Colour management – Default RGB colour space – sRGBIEC International System of Units zone
Units of luminance
SI derived units