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

Definition

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1 lm = 1 cd·sr = 1 cd·m²·m^–2

SI multiples

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Explanation

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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 $4\backslash pi$ 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 the article on incandescent light bulbs for the specific efficiency of various types of electric light sources.

SI photometry units

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See also

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• Video projector for a discussion on lumen ratings of projectors.

Photometry | Units of luminous flux | SI derived units

Лумен | Lumen | Lumen | Lumen | Lumen (Einheit) | Lumen | Lumen (physique) | Lumen | לומן | Lumen (natuurkunde) | ルーメン | Lumen | Lumen | Lumen | Lúmen | Люмен | Лумен | Luumen | Lumen