Luminous energy
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More proper wording
In [[photometry]], '''luminous energy''' is the perceived [[energy]] of [[light]]. This is sometimes also called the '''quantity of light'''.
Luminous energy is not the same as the [[radiant energy]], the corresponding objective [[physical quantity]]. This is because the human [[eye]] can only see light in the [[visible spectrum]] and has different sensitivities to [[light]] of different [[wavelength]]s within the spectrum. When adapted for bright conditions ([[photopic vision]]), the eye is most sensitive to light at a [[wavelength]] of 555 [[metre|nm]]. Light with the same power at longer or shorter wavelengths has a lower luminous energy.
==Units==
The [[SI]] unit of luminous energy is the [[lumen]] [[second]], which is unofficially known as the [[Talbot (photometry)|Talbot]] in honor of [[William Henry Fox Talbot]].
In other [[systems of units]], luminous energy may be expressed in basic units of [[energy]].
==See also==
*[[Radiant energy]]
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[[Category:Physical quantity]]
[[Category:Photometry]]
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