The candela per square metre (symbol: cd/m
2) is the unit of
luminance in the
International System of Units (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
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 human e ...
, and the
square metre, 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 ope ...
. 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 spec for monitors targets . Typically, monitors calibrated for
SDR broadcast or studio color grading should have a brightness of . Most consumer desktop
liquid crystal displays 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
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. The symbol for the apostilb ...
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 corr ...
s
*π×10
3 skots
*π×10
7 brils
*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