Lux

<p>The lux (symbol: lx) is the unit of <a href="/facts/Illuminance/6Dj4pKmu">illuminance</a>, or <a href="/facts/Luminous_flux/Sfya3RXh">luminous flux</a> per unit area, in the <a href="/facts/International_System_of_Units/S7YLglNz">International System of Units</a> (SI). It is equal to one <a href="/facts/Lumen_(unit)/DbdghwnN">lumen</a> per square metre. In <a href="/facts/Photometry_(optics)/eo6J7qj3">photometry</a>, this is used as a measure of the <a href="/facts/Irradiance/fgHwu7uh">irradiance</a>, as perceived by the spectrally unequally responding human eye, of <a href="/facts/Light/jeofpMn4">light</a> that hits or passes through a surface. It is analogous to the <a href="/facts/Radiometry/w9j9PXSB">radiometric</a> unit <a href="/facts/Irradiance/fgHwu7uh">watt per square metre</a>, but with the power at each <a href="/facts/Wavelength/kcJU0ymz">wavelength</a> weighted according to the <a href="/facts/Luminosity_function/7H2G30dE">luminosity function</a>, a model of <a href="/facts/Human/rlcTENsr">human</a> visual brightness perception, standardized by the CIE and <a href="/facts/International_Organization_for_Standardization/IacYR7Yg">ISO</a>. In English, "lux" is used as both the singular and plural form.
The word is derived from the <a href="/facts/Latin/pM3Kge85">Latin</a> word for "light", lux.
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Lux open-in-new

Lux