Luminous efficacy is a measure of how effectively a light supply produces visible light. It's the ratio of luminous flux to power, measured in lumens per watt in the Worldwide System of Units (SI). Depending on context, the ability may be either the radiant flux of the supply's output, or it may be the overall power (electric energy, chemical vitality, or others) consumed by the supply. Which sense of the term is meant should often be inferred from the context, and is typically unclear. Not all wavelengths of light are equally seen, or equally effective at stimulating human imaginative and prescient, due to the spectral sensitivity of the human eye; radiation within the infrared and ultraviolet components of the spectrum is useless for illumination. The luminous efficacy of a source is the product of how properly it converts power to electromagnetic radiation, and the way well the emitted radiation is detected by the human eye. Luminous efficacy may be normalized by the utmost attainable luminous efficacy to a dimensionless amount known as luminous effectivity.

My web page EcoLight reviews