Category:Photometry

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Photometry is the science of measurement of light, in terms of its apparent brightness to the human eye. It is distinct from radiometry, which is the science of measurement of light in terms of absolute power. Note that this term is used differently in astronomy. For information on the astronomical method, see Photometry (astronomy). Lua error in package.lua at line 80: module 'Module:Category main article' not found.

SI photometry quantities
Quantity Unit Dimension Notes
Name Symbol[nb 1]r Name Symbol Symbol
Luminous energy Qv [nb 2] lumen second lm⋅s TJ [nb 3] Units are sometimes called talbots.
Luminous flux / luminous power Φv [nb 2] lumen (= cd⋅sr) lm J [nb 3] Luminous energy per unit time.
Luminous intensity Iv candela (= lm/sr) cd J [nb 3] Luminous power per unit solid angle.
Luminance Lv candela per square metre cd/m2 L−2J Luminous power per unit solid angle per unit projected source area. Units are sometimes called nits.
Illuminance Ev lux (= lm/m2) lx L−2J Luminous power incident on a surface.
Luminous exitance / luminous emittance Mv lux lx L−2J Luminous power emitted from a surface.
Luminous exposure Hv lux second lx⋅s L−2TJ
Luminous energy density ωv lumen second per cubic metre lm⋅s⋅m−3 L−3TJ
Luminous efficacy η [nb 2] lumen per watt lm/W M−1L−2T3J Ratio of luminous flux to radiant flux or power consumption, depending on context.
Luminous efficiency / luminous coefficient V 1
See also: SI · Photometry · Radiometry

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