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EntityQ484092· pop 72· linked from 205 articles

lumen

Also known as lm

SI unit of luminous flux

AI overview

A lumen is the standard scientific unit used to measure how much visible light a source produces in all directions. It matters because it helps people compare the brightness of different light sources—like light bulbs—in a consistent, standardized way.

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Wikidata facts

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conversion to SI unit: 1
unit symbol: lm
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Article

The lumen (symbol: lm) is the SI unit of luminous flux, which quantifies the perceived power of visible light emitted by a source. Luminous flux differs from power (radiant flux), which encompasses all electromagnetic waves emitted, including non-visible ones such as thermal radiation (infrared). By contrast, luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to various wavelengths; this weighting is standardized by the CIE and ISO.

The lumen is defined as equivalent to one candela-steradian (symbol cd·sr):