Lumen (unit)

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The lumen (symbol: lm) is the SI unit of luminous flux.

Contents

[edit] Definition

1 lm = 1 cd·sr = 1 cd·m2·m–2

[edit] SI multiples

Multiple Name Symbol Multiple Name Symbol
100 lumen lm      
101 decalumen dalm 10–1 decilumen dlm
102 hectolumen hlm 10–2 centilumen clm
103 kilolumen klm 10–3 millilumen mlm
106 megalumen Mlm 10–6 microlumen µlm
109 gigalumen Glm 10–9 nanolumen nlm
1012 teralumen Tlm 10–12 picolumen plm
1015 petalumen Plm 10–15 femtolumen flm
1018 exalumen Elm 10–18 attolumen alm
1021 zettalumen Zlm 10–21 zeptolumen zlm
1024 yottalumen Ylm 10–24 yoctolumen ylm

[edit] Explanation

If a light source emits one candela of luminous intensity into a solid angle of one steradian, the total luminous flux emitted into that solid angle is one lumen. Alternatively, an isotropic one-candela light source emits a total luminous flux of exactly 4π lumens. The lumen can be thought of casually as a measure of the total "amount" of visible light emitted.

A standard 100 watt incandescent light bulb emits approximately 1700 lumens. See luminous efficacy for the specific efficiency of various types of electric light sources.

[edit] SI photometry units

[edit]

SI photometry units
Quantity Symbol SI unit Abbr. Notes
Luminous energy Qv lumen second lm·s units are sometimes called Talbots
Luminous flux F lumen (= cd·sr) lm also called luminous power
Luminous intensity Iv candela (= lm/sr) cd an SI base unit
Luminance Lv candela per square metre cd/m2 units are sometimes called nits
Illuminance Ev lux (= lm/m2) lx Used for light incident on a surface
Luminous emittance Mv lux (= lm/m2) lx Used for light emitted from a surface
Luminous efficacy   lumen per watt lm/W ratio of luminous flux to radiant flux; maximum possible is 683.002


[edit] See also

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