Stilb (unit)
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Thestilb(sb) is theCGSunit ofluminancefor objects that are not self-luminous. It is equal to onecandelaper square centimeter or 104nits(candelas per square meter). The name was coined by the French physicistAndré Blondelaround 1920.[1]It comes from the Greek wordstilbein(στίλβειν), meaning 'to glitter'.
It was in common use in Europe up toWorld 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terms such as candle per square inch and candle per square meter were more common.[2]The unit has since largely been replaced by the SI unit:candela per square meter.The current national standard for SI in the United States discourages the use of the stilb.[3]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
[edit]| cd/m2(SIunit) ≡ nit≡ lm/m2/sr |
stilb(sb)(CGSunit) ≡ cd/cm2 |
apostilb(asb) ≡ blondel |
bril | skot(sk) | lambert(L) | foot-lambert(fL) = 1 ⁄πcd/ft2 | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 cd/m2 | = | 1 | 10−4 | π ≈ 3.142 |
107π ≈ 3.142×107 |
103π ≈ 3.142×103 |
10−4π ≈ 3.142×10−4 |
0.30482π ≈ 0.2919 | ||
| 1 sb | = | 104 | 1 | 104π ≈ 3.142×104 |
1011π ≈ 3.142×1011 |
107π ≈ 3.142×107 |
π ≈ 3.142 |
30.482π ≈ 2919 | ||
| 1 asb | = | 1 ⁄π ≈ 0.3183 |
10−4⁄π ≈ 3.183×10−5 |
1 | 107 | 103 | 10−4 | 0.30482 ≈ 0.09290 | ||
| 1 bril | = | 10−7⁄π ≈ 3.183×10−8 |
10−11⁄π ≈ 3.183×10−12 |
10−7 | 1 | 10−4 | 10−11 | 0.30482×10−7 ≈ 9.290×10−9 | ||
| 1 sk | = | 10−3⁄π ≈ 3.183×10−4 |
10−7⁄π ≈ 3.183×10−8 |
10−3 | 104 | 1 | 10−7 | 0.30482×10−3 ≈ 9.290×10−5 | ||
| 1 L | = | 104⁄π ≈ 3183 |
1 ⁄π ≈ 0.3183 |
104 | 1011 | 107 | 1 | 0.30482×104 ≈ 929.0 | ||
| 1 fL | = | 1 ⁄ 0.30482⁄π ≈ 3.426 |
1 ⁄ 30.482⁄π ≈ 3.426×10−4 |
1 ⁄ 0.30482 ≈ 10.76 |
107⁄ 0.30482 ≈ 1.076×108 |
103⁄ 0.30482 ≈ 1.076×104 |
10−4⁄ 0.30482 ≈ 1.076×10−3 |
1 | ||
| Quantity | Unit | Dimension [nb 1] |
Notes | ||
|---|---|---|---|---|---|
| Name | Symbol[nb 2] | Name | Symbol | ||
| Luminous energy | Qv[nb 3] | lumen second | lm⋅s | T⋅J | The lumen second is sometimes called thetalbot. |
| Luminous flux,luminous power | Φv[nb 3] | lumen(= candelasteradian) | lm (= cd⋅sr) | J | Luminous energy per unit time |
| Luminous intensity | Iv | candela(= lumen per steradian) | cd(= lm/sr) | J | Luminous flux per unitsolid angle |
| Luminance | Lv | candela per square metre | cd/m2(= lm/(sr⋅m2)) | L−2⋅J | Luminous flux per unit solid angle per unitprojectedsource area. The candela per square metre is sometimes called thenit. |
| Illuminance | Ev | lux(= lumen per square metre) | lx(= lm/m2) | L−2⋅J | Luminous fluxincidenton a surface |
| Luminous exitance,luminous emittance | Mv | lumen per square metre | lm/m2 | L−2⋅J | Luminous fluxemittedfrom a surface |
| Luminous exposure | Hv | lux second | lx⋅s | L−2⋅T⋅J | Time-integrated illuminance |
| Luminous energy density | ωv | lumen second per cubic metre | lm⋅s/m3 | L−3⋅T⋅J | |
| Luminous efficacy(of radiation) | K | lumen perwatt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux toradiant flux |
| Luminous efficacy(of a source) | η[nb 3] | lumen perwatt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux to power consumption |
| Luminous efficiency,luminous coefficient | V | 1 | Luminous efficacy normalized by the maximum possible efficacy | ||
| See also: | |||||
- ^The symbols in this column denotedimensions;"L","T"and"J"are for length, time and luminous intensity respectively, not the symbols for theunitslitre, tesla and joule.
- ^Standards organizationsrecommend that photometric quantities be denoted with a subscript "v" (for "visual" ) to avoid confusion with radiometric orphotonquantities. For example:USA Standard Letter Symbols for Illuminating EngineeringUSAS Z7.1-1967, Y10.18-1967
- ^abcAlternative symbols sometimes seen:Wfor luminous energy,PorFfor luminous flux, andρfor luminous efficacy of a source.
See also
[edit]References
[edit]- ^Parry Moon. "System of photometer concepts", in theJournal 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.
Further reading
[edit]- StilbatA Dictionary of Units of Measurement,Russ Rowlett and the University of North Carolina at Chapel Hill. Accessed June 2008.
- Stilbat Sizes.com. Accessed June 2008.
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