The lambert (symbol L, la or Lb) is a non-
SI metric unit
The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Internati ...
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 withi ...
named for
Johann Heinrich Lambert
Johann Heinrich Lambert (, ''Jean-Henri Lambert'' in French; 26 or 28 August 1728 – 25 September 1777) was a polymath from the Republic of Mulhouse, generally referred to as either Swiss or French, who made important contributions to the subjec ...
(1728–1777), a Swiss mathematician, physicist and astronomer. A related unit of luminance, the
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 ...
, is used in the lighting, cinema and flight simulation industries. The SI unit is the
candela per square metre
The candela per square metre (symbol: cd/m2) is the unit of luminance in the International System of Units (SI). The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area. The nit (symbol: n ...
(cd/m
2).
Definition
1 lambert (L) =
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 to ...
per
square centimetre (0.3183 cd/cm
2) or
cd m
−2
See also
Other units of luminance:
*
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 i ...
(asb)
*
Blondel (blondel)
*
Bril (bril)
*
Nit (nit)
*
Stilb (sb)
*
Skot (sk)
{{SI light units
References
"Lighting Design Glossary: Luminance" at ''Schorsch Lighting Design Knowledgebase''
Units of luminance
Non-SI metric units