speed of light
[3.13] (See Spectral Parameters.)
photometric brightness
[3.5.9] (See luminance.)
nit (nt)
[3.5.8] (See SI unit of luminance.)
talbot (T)
[3.9.2] (See lumen‑second.)
luminous efficacy of a source
[3.11] The total emitted luminous flux divided by the total source electrical input power; expressed in lumens per watt (lm/W). Note 1: The term luminous efficacy can be applied to […]
luminous efficacy of radiant flux
[3.10.4] The quotient of the total luminous flux by the total radiant flux. It is expressed in lumens per watt (lm/W).
CIE scotopic luminous efficiency function
[3.10.3] V’ (Λ) The spectral luminous efficiency function for scotopic vision, adopted by the International Commission on Illumination (CIE) in 1951. (See Table T-7.) NOTE: This term and its definition […]
CIE 1988 2° modified spectral luminous efficiency function for photopic vision
[3.10.2.1] VM(λ) A supplemental modification of V(λ), adopted by the International Commission on Illumination (CIE) in 1990.* This function is principally of interest in the visual sciences. (See Table T-9.) NOTE: […]
CIE photopic luminous efficiency function
[3.10.2] V(λ) The spectral luminous efficiency function for photopic vision. It was adopted in 1924 by the International Commission on Illumination (CIE) and in 1970* by the International Committee […]
spectral luminous efficiency of radiant flux
[3.10.1] The ratio of the luminous efficacy for a given wavelength to the value at the wavelength of maximum luminous efficacy. It is dimensionless. Note: The term spectral luminous efficiency […]