Lumen_second

Lumen second

Lumen second

SI derived unit of luminous energy

In photometry, the lumen second (lm⋅s) is the unit of luminous energy in the International System of Units (SI). It is based on the lumen, the SI unit of luminous flux, and the second, the SI base unit of time.

Quick Facts Unit system, Unit of ...

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.[1] The talbot is exactly equal to the lumen second:

1 T = 1 lm⋅s

The use of the symbol T for talbots conflicts with T as the symbol for the tesla, the SI unit of magnetic flux density.

The photometric unit lumerg[1] or lumberg,[2] 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 radiometric unit joule, so that 107 lumerg = 1 lm⋅s.[1]

More information Quantity, Unit ...
  1. [N 1]
    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.
  2. [N 2]
    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
  3. [N 3]
    Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ for luminous efficacy of a source.

References

  1. [1]
    Loyd Ancile Jones. Colorimetry: Preliminary draft of a report on nomenclature and definitions. Journal of the Optical Society of America, Volume 27, page 211 (June 1937): “Referring again to Table I, terms (21) and (22) represent names for units which the committee has voted to adopt. The decision was almost unanimous in the case of recommending talbot as a psychophysical correlate of joule. The vote on lumerg as the psychophysical correlate of the erg was less unanimous.”
  2. [2]
    Jerrard, H. G.; McNeill, D. B. (2012). Dictionary of Scientific Units: Including dimensionless numbers and scales (6th ed.). Springer Science & Business Media. p. 92. ISBN 9789401122948.
Share this article:

This article uses material from the Wikipedia article Lumen_second, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.