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{{Short description|SI derived unit of luminous energy}}
In [[photometry (optics)|photometry]], the '''lumen second''' ('''lm ⋅ s''') is the [[SI derived unit]] of [[luminous energy]]. It is based on the [[lumen (unit)|lumen]], the SI unit of [[luminous flux]], and the [[second]], the [[SI base unit]] of time.▼
{{Infobox Unit
| name = Lumen second
| standard = [[SI]]
| quantity = [[luminous energy]]
| symbol = lm·s
}}
▲In [[photometry (optics)|photometry]], the '''lumen second''' ('''lm ⋅ slm⋅s''') is the unit of [[SIluminous derived unitenergy]] ofin the [[luminousInternational energySystem of Units]] (SI). It is based on the [[lumen (unit)|lumen]], the SI unit of [[luminous flux]], and the [[second]], the [[SI base unit]] of time.
 
The lumen second is sometimes called the '''talbot''' (symbol '''T'''). This name was coined in 1937 by the Committee on Colorimetry, [[Optical Society of America]], in honor of the early [[photographer]] [[William Fox Talbot]].<ref name="Loyd_1937_Nomenclature" /> The talbot is exactly equal to the lumen second:
:1 T = 1 lm ⋅ slm⋅s
 
The use of the symbol T for talbots conflicts with T as the symbol for the [[tesla (unit)|tesla]], the SI unit of magnetic flux density.
 
The photometric unit '''lumerg'''<!--ref Noname="Loyd_1937_Nomenclature"/> typoor here'''lumberg''',<ref>{{cite unlessbook the|title=Dictionary typoof isScientific withUnits: JonesIncluding already!dimensionless -->,numbers alsoand scales |first1=H. G. |last1=Jerrard |first2=D. B. |last2=McNeill |edition=6th |publisher=Springer Science & Business Media |year=2012 |isbn=9789401122948 |page=92 |url=https://books.google.com/books?id=tjz6CAAAQBAJ&dq=loudness+lumberg&pg=PA92 }}</ref> proposed by the Committee on Colorimetry in 1937, correlates with the old [[CGS]] unit [[erg]] in the same way that the lumen second correlates with the [[radiometry|radiometric]] unit [[joule]], so that {{nowrap|1=10<sup>7</sup> lumerg<!-- No typo here, unless the typo is with LA Jones already! --> &nbsp;= &nbsp;1 &nbsp;lm⋅s}}.<ref name="Loyd_1937_Nomenclature">[[Loyd Ancile Jones|Loyd A. Jones]]. ''Colorimetry: Preliminary draft of a report on nomenclature and definitions''. Journal of the [[Optical Society of America]], Volume&nbsp;27, page&nbsp;211 (June&nbsp;1937): “Referring again to Table&nbsp;I, terms&nbsp;(21) and (22) represent names for units which the committee has voted to adopt. The decision was almost unanimous<!-- votes: 16:2 --> in the case of recommending talbot as a [[Psychophysics|psychophysical]] correlate of [[joule]]. The vote on lumerg<!-- No typo here, unless the typo is with Jones already! --> as the psychophysical correlate of the [[erg]] was less unanimous<!-- votes: 11:9 -->.”</ref>▼
An older name for the lumen second was the '''lumberg'''<!-- no typo here -->.{{Citation needed|date=August 2011}}<!-- I find lumberg listed in many places, including other language WPs, but could not track down the origin of this unit. It is said to be an older name for what later became the talbot (without giving dates). However, given the similarity with lumerg (note the missing "b", which is not a typo), which could be tracked back to the meeting of the committee on colorimetry in 1937, and which is defined as 10^-7 talbot, it could well be, that lumberg is just the result of a typo. However, it is also possible that Loyd Ancile Jones publication "Preliminary draft of a report on nomenclature and definitions" is the origin of a typo the other way, and that what he spelled as lumerg should have been lumberg. Then, both could well be the same, and with the facts gone lost and both units no longer in use, lum[b]erg might have started to appear just as an older name for talbot. -->
 
▲The photometric unit '''lumerg'''<!-- No typo here, unless the typo is with Jones already! -->, also proposed by the Committee on Colorimetry in 1937, correlates with the old [[CGS]] unit [[erg]] in the same way that the lumen second correlates with the [[radiometry|radiometric]] unit [[joule]], so that 10<sup>7</sup> lumerg<!-- No typo here, unless the typo is with LA Jones already! --> = 1 lm⋅s.<ref name="Loyd_1937_Nomenclature">[[Loyd Ancile Jones|Loyd A. Jones]]. ''Colorimetry: Preliminary draft of a report on nomenclature and definitions''. Journal of the [[Optical Society of America]], Volume&nbsp;27, page&nbsp;211 (June&nbsp;1937): “Referring again to Table&nbsp;I, terms&nbsp;(21) and (22) represent names for units which the committee has voted to adopt. The decision was almost unanimous<!-- votes: 16:2 --> in the case of recommending talbot as a [[Psychophysics|psychophysical]] correlate of [[joule]]. The vote on lumerg<!-- No typo here, unless the typo is with Jones already! --> as the psychophysical correlate of the [[erg]] was less unanimous<!-- votes: 11:9 -->.”</ref>
 
{{SI_light units}}
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<references />
 
[[Category:Photometry]]▼
[[Category:Units of luminous energy]]
▲[[Category:PhotometrySI derived units]]
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