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 wit ...
in the
International System of Units
The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official s ...
(SI). The unit is based on the
candela
The candela (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 to radi ...
, the SI unit of
luminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the huma ...
, 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 measure of a region's size on a 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 open surface or the boundary of a three-di ...
.
The nit (symbol: nt) is a deprecated 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
A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signa ...
. The
sRGB spec for
monitors targets . Typically, monitors calibrated for
SDR broadcast or studio
color grading
Color grading is a post-production process common to filmmaking and video editing of altering the appearance of an image for presentation in different environments on different devices. Various attributes of an image such as contrast (vision), ...
should have a brightness of . Most consumer desktop
liquid crystal display
A liquid-crystal display (LCD) is a flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liq ...
s have luminances of 200 to 300 cd/m
2.
HDR displays range from around 400 to 2500 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
apostilb
The apostilb is an obsolete unit of luminance. The SI unit of luminance is the candela per square metre (cd/m2). In 1942 Parry Moon proposed to rename the apostilb the blondel, after the French physicist André Blondel
André-Eugène Blondel (2 ...
s
*0.292
foot-lambert
A foot-lambert or footlambert (fL, sometimes fl or ft-L) is a unit of luminance in United States customary units and some other unit systems. A foot-lambert equals 1/π or 0.3183 candela per square foot, or 3.426 candela per square meter (the corre ...
s
*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 Southern Netherlands, Flemish painter ...
s
*1 nit
See also
*
Orders of magnitude (luminance)
As visual perception varies logarithmically, it is helpful to have an appreciation of both illuminance and luminance by orders of magnitude.
Illuminance
To help compare different orders of magnitude, the following list describes various source in ...
*
Photometry (optics)
Photometry is a branch of optics that deals with measuring light
Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectr ...
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