What is "lumen second"

alt. (context physics English) A derived SI unit of luminous energy. n. (context physics English) A derived SI unit of luminous energy.

In photometry, the lumen second (lm s or lm⋅s) is the SI derived unit of luminous energy. It is based on the 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. The Talbot is exactly equal to the lumen second:

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

An older name for the lumen second was the lumberg .

The photometric unit lumerg , 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 radiometric unit joule, so that 10 lumerg = 1 lm⋅s.