Stilb (unit)
The stilb (sb) is the CGS unit of luminance for objects that are not self-luminous. It is equal to one candela per square centimeter or 104 nits (candelas per square meter). The name was coined by the French physicist André Blondel around 1920.[1] It comes from the Greek word Script error: No such module "Lang". (Template:Wikt-lang), meaning 'to glitter'.
It was in common use in Europe up to World War I. In North America self-explanatory terms such as candle per square inch and candle per square meter were more common.[2] The unit has since largely been replaced by the SI unit: candela per square meter. The current national standard for SI in the United States discourages the use of the stilb.[3]
Unit conversion
Template:Luminance conversions Script error: No such module "anchor".
| Quantity | Unit | Dimension [nb 1] |
Notes | ||
|---|---|---|---|---|---|
| Name | Symbol[nb 2] | Name | Symbol | ||
| Luminous energy | QvScript error: No such module "Check for unknown parameters".[nb 3] | lumen second | lm⋅s | T⋅J | The lumen second is sometimes called the talbot. |
| Luminous flux, luminous power | ΦvScript error: No such module "Check for unknown parameters".[nb 3] | lumen (= candela steradian) | lm (= cd⋅sr) | J | Luminous energy per unit time |
| Luminous intensity | IvScript error: No such module "Check for unknown parameters". | candela (= lumen per steradian) | cd (= lm/sr) | J | Luminous flux per unit solid angle |
| Luminance | LvScript error: No such module "Check for unknown parameters". | candela per square metre | cd/m2 (= lm/(sr⋅m2)) | L−2⋅J | Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit. |
| Illuminance | EvScript error: No such module "Check for unknown parameters". | lux (= lumen per square metre) | lx (= lm/m2) | L−2⋅J | Luminous flux incident on a surface |
| Luminous exitance, luminous emittance | MvScript error: No such module "Check for unknown parameters". | lumen per square metre | lm/m2 | L−2⋅J | Luminous flux emitted from a surface |
| Luminous exposure | HvScript error: No such module "Check for unknown parameters". | lux second | lx⋅s | L−2⋅T⋅J | Time-integrated illuminance |
| Luminous energy density | ωvScript error: No such module "Check for unknown parameters". | lumen second per cubic metre | lm⋅s/m3 | L−3⋅T⋅J | |
| Luminous efficacy (of radiation) | KScript error: No such module "Check for unknown parameters". | lumen per watt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux to radiant flux |
| Luminous efficacy (of a source) | Template:Mvar[nb 3] | lumen per watt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux to power consumption |
| Luminous efficiency, luminous coefficient | Template:Mvar | 1 | Luminous efficacy normalized by the maximum possible efficacy | ||
| See also: Template:Hlist | |||||
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- ↑ The symbols in this column denote dimensions; "L", "T" and "J" are for length, time and luminous intensity respectively, not the symbols for the units litre, tesla and joule.
- ↑ Standards organizations recommend that photometric quantities be denoted with a subscript "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
- ↑ a b c Alternative symbols sometimes seen: Template:Mvar for luminous energy, Template:Mvar or Template:Mvar for luminous flux, and Template:Mvar for luminous efficacy of a source.
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See also
References
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- ↑ Parry Moon. "System of photometer concepts", in the Journal of the Optical Society of America, volume 32, number 6 (June 1942). – Page 355: "The lumen was proposed by Blondel in 1894 and is now universally accepted. The names, phot and stilb were likewise coined by Blondel (1921) and are in general use on the Continent."
- ↑ American Standard Definitions of Electrical Terms, New York: American Institute of Electrical Engineers, 1941.
- ↑ IEEE/ASTM SI 10-2002. American National Standard for Use of the International System of Units (SI): The Modern Metric System. New York: IEEE, 30 December 2002. See Section 3.3.3.
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