The candela per square metre (symbol: cd/m
2) is the unit of
luminance 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 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. 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
apostilbs
*0.292
foot-lamberts
*π×10
3 skots
*π×10
7 brils
*1 nit
See also
*
Orders of magnitude (luminance)
*
Photometry (optics)
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