On September 1, 2010, European Union legislation came into force mandating that lighting equipment must be labelled " primarily " in terms of luminous flux ( lm ), instead of electric power ( W ).
22.
Like the photometric definition, it is related to the luminous flux density in a particular direction, which is radiant flux density weighted by the luminosity function ( " ? " ) of the CIE Standard Observer.
23.
One can think of luminous flux ( measured in lumens ) as a measure of the total " amount " of visible light present, and the illuminance as a measure of the intensity of illumination on a surface.
24.
A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so illuminance ( lux ) is inversely proportional to area when the luminous flux ( lumens ) is held constant.
25.
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.
26.
It differs from radiant flux, the measure of the total power of electromagnetic radiation ( including infrared, ultraviolet, and visible light ), in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.
27.
The manufacturer of each selected luminaire will be required to commission third-party testing, each being tested for : total luminous flux, luminaire efficacy, correlated color temperature, color rendering index, steady state package / module / array temperature, and maximum power supply case.
28.
In LED lighting, "'lumen maintenance "'is the luminous flux remaining ( expressed as a percentage of the initial output ) at any selected elapsed operating time . "'Lumen depreciation "'is the luminous flux lost over time, and thus the complement of lumen maintenance.
29.
In LED lighting, "'lumen maintenance "'is the luminous flux remaining ( expressed as a percentage of the initial output ) at any selected elapsed operating time . "'Lumen depreciation "'is the luminous flux lost over time, and thus the complement of lumen maintenance.
30.
These are used in several applications, including new generation tanning lamp systems, whereby a 100 watt lamp ( e . g ., F71T12BP ) can be lit using 90 watts of actual power while obtaining the same luminous flux ( measured in lumens ) as magnetic ballasts.
