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Not all wavelengths of light are equally visible, or equally effective at stimulating human vision, due to the spectral sensitivity of the human eye; radiation in the infrared and ultraviolet parts of the spectrum is useless for illumination. The luminous efficacy of a source is the product of how well it converts energy to electromagnetic ...
The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function. The lumen is defined to be unity for a radiant energy of 1/683 W at a frequency of 540 THz , which corresponds to a standard air wavelength of 555.016 nm rather than 555 nm , which is the peak of the ...
Historically light was measured in the units of luminous intensity , luminance (candelas/m 2) and illuminance (lumen/m 2). After the discovery of ipRGCs in 2002 additional units of light measurement have been researched in order to better estimate the impact of different inputs of the spectrum of light on various photoreceptors. However, due to ...
Mesopic vision, sometimes also called twilight vision, is a combination of photopic and scotopic vision under low-light (but not necessarily dark) conditions. [1] Mesopic levels range approximately from 0.01 to 3.0 cd/m 2 in luminance.
Light with the same radiant intensity at other wavelengths has a lower luminous intensity. The curve which represents the response of the human eye to light is a defined standard function y (λ) or V (λ) established by the International Commission on Illumination (CIE, for Commission Internationale de l'Éclairage ) and standardized in ...
Several measures of light are commonly known as intensity: Radiant intensity , a radiometric quantity measured in watts per steradian (W/sr) Luminous intensity , a photometric quantity measured in lumens per steradian (lm/sr), or candela (cd)
Factor ()Multiple Value Item 0 0 lux 0 lux Absolute darkness 10 −4: 100 microlux 100 microlux: Starlight overcast moonless night sky [1]: 140 microlux: Venus at brightest [1]: 200 microlux
Landscape lighting or garden lighting refers to the use of outdoor illumination of private gardens and public landscapes; for the enhancement and purposes of safety, nighttime aesthetics, accessibility, security, recreation and sports, and social and event uses. Light pollution is exacerbated by excessive, misdirected, or obtrusive use of light.