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Luminous efficacy can be normalized by the maximum possible luminous efficacy to a dimensionless quantity called luminous efficiency.The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.
lux (= lumen per square metre) lx (= lm/m 2) L −2 ⋅J: Luminous flux incident on a surface Luminous exitance, luminous emittance M v: lumen per square metre lm/m 2: L −2 ⋅J: Luminous flux emitted from a surface Luminous exposure: H v: lux second: lx⋅s L −2 ⋅T⋅J: Time-integrated illuminance Luminous energy density ω v: lumen ...
The same 1,000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux. In equation form, 1 lx = 1 lm/m 2. A source radiating a power of one watt of light in the color for which the eye is most efficient (a wavelength of 555 nm, in the green region of the optical spectrum) has luminous flux of 683 lumens.
Φ v is the luminous flux, in lumens; Φ e,λ is the spectral radiant flux, in watts per nanometre; y (λ), also known as V(λ), is the luminosity function, dimensionless; λ is the wavelength, in nanometres. Formally, the integral is the inner product of the luminosity function with the spectral power distribution. [2]
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines. An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally ...
I e is the radiant intensity in watts per steradian (W/sr), y ¯ ( λ ) {\textstyle {\overline {y}}(\lambda )} is the standard luminosity function . If more than one wavelength is present (as is usually the case), one must sum or integrate over the spectrum of wavelengths present to get the luminous intensity:
lumen per square metre lm/m 2: L −2 ⋅J: Luminous flux emitted from a surface Luminous exposure: H v: lux second: lx⋅s L −2 ⋅T⋅J: Time-integrated illuminance Luminous energy density ω v: lumen second per cubic metre lm⋅s/m 3: L −3 ⋅T⋅J: Luminous efficacy (of radiation) K: lumen per watt: lm/W: M −1 ⋅L −2 ⋅T 3 ⋅J ...
lumen per square metre lm/m 2: L −2 ⋅J: Luminous flux emitted from a surface Luminous exposure: H v: lux second: lx⋅s L −2 ⋅T⋅J: Time-integrated illuminance Luminous energy density ω v: lumen second per cubic metre lm⋅s/m 3: L −3 ⋅T⋅J: Luminous efficacy (of radiation) K: lumen per watt: lm/W: M −1 ⋅L −2 ⋅T 3 ⋅J ...