The spatially directed emission of LEDs often makes it easier to avoid substantial light losses in fixtures. While some fixtures are essentially lossless, others completely spoil the efficiency. Obviously, it makes sense to optimize not only the light source, but also the fixture. Note that the luminous efficacy of a lighting device – for example, a ceiling lamp for a living room or a street lamp – can be substantially lower than that of the used light source, if much of the generated light is lost e.g. The high efficacy of a light source can be spoiled with a poor lamp design! The same luminous flux could be generated with a lamp based on light emitting diodes (LEDs) with a power consumption well below 10 W, since it is much more efficacious. For example, a 60-W light bulb ( incandescent lamp) may emit 900 lumen, which leads to a luminous efficacy of 15 lm/W. The more common definition is the luminous flux divided by the electrical power consumption of a light source.If one divides by the radiant flux, the result only depends on the shape of the optical spectrum of the light source in conjunction with the applied luminosity function, which quantifies the wavelength-dependent sensitivity of the standard human eye.In both cases, one obtains units of lumen per watt (lm/W), but the meaning is of course different: The luminous efficacy of a light source is its generated luminous flux divided either by its radiant flux or by its electrical power consumption. How to cite the article suggest additional literature Encyclopedia > letter L > Luminous efficacy and efficiency Luminous Efficacy and Efficiencyĭefinition: the luminous flux of a light source divided by its the radiant power or its electrical consumption (efficacy) the ratio of reached efficacy to the theoretically possible efficacy (luminous efficiency)Ĭategory: light detection and characterization
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