Lambert (unit)
From Wikipedia, the free encyclopedia
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 | Unit | Dimension | Notes | |||||
|---|---|---|---|---|---|---|---|---|
| Name | Symbol[nb 1] | Name | Symbol | Symbol | ||||
| Luminous energy | Qv [nb 2] | lumen second | lm⋅s | T⋅J [nb 3] | units are sometimes called talbots | |||
| Luminous flux | Φv [nb 2] | lumen (= cd⋅sr) | lm | J [nb 3] | 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. For example: USA Standard Letter Symbols for Illuminating Engineering USAS Z7.1-1967, Y10.18-1967
- ↑ 2.0 2.1 2.2 Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ or K for luminous efficacy.
- ↑ 3.0 3.1 3.2 "J" here is the symbol for the dimension of luminous intensity, not the symbol for the unit joules.
References
This article is issued from Wikipedia. The text is available under the Creative Commons Attribution/Share Alike; additional terms may apply for the media files.