Lambert (unit)
The lambert (symbol L, la or Lb) is a non-SI unit of luminance named for Johann Heinrich Lambert (1728–1777), a Swiss mathematician, physicist and astronomer. A related unit of luminance, the foot-lambert, is used in the lighting, cinema and flight simulation industries. The SI unit is the candela per square metre (cd/m²).
Definition
1 lambert (L) = 
candela per square centimetre (0.3183 cd/cm²) or 
cd m-2
See also
Other units of luminance:
| Quantity | Symbol[nb 1] | SI unit | Symbol | Dimension | Notes | |||
|---|---|---|---|---|---|---|---|---|
| Luminous energy | Qv [nb 2] | lumen second | lm⋅s | T⋅J | units are sometimes called talbots | |||
| Luminous flux | Φv [nb 2] | lumen (= cd⋅sr) | lm | J | also called luminous power | |||
| Luminous intensity | Iv | candela (= lm/sr) | cd | J [nb 3] | an SI base unit, luminous flux per unit solid angle | |||
| Luminance | Lv | candela per square metre | cd/m2 | L−2⋅J | units are sometimes called nits | |||
| Illuminance | Ev | lux (= lm/m2) | lx | L−2⋅J | used for light incident on a surface | |||
| Luminous emittance | Mv | lux (= lm/m2) | lx | L−2⋅J | used for light emitted from a surface | |||
| Luminous exposure | Hv | lux second | lx⋅s | L−2⋅T⋅J | ||||
| Luminous energy density | ωv | lumen second per metre3 | lm⋅s⋅m−3 | L−3⋅T⋅J | ||||
| Luminous efficacy | η [nb 2] | lumen per watt | lm/W | M−1⋅L−2⋅T3⋅J | ratio of luminous flux to radiant flux | |||
| Luminous efficiency | V | 1 | also called luminous coefficient | |||||
| See also: SI · Photometry · Radiometry | ||||||||
- ^ Standards organizations recommend that photometric quantities be denoted with a suffix "v" (for "visual") to avoid confusion with radiometric or photon quantities.
- ^ a b c Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ or K for luminous efficacy.
- ^ "J" is the recommended symbol for the dimension of luminous intensity in the International System of Units.