product of spectral luminous efficiency and maximum luminous efficacy for a specified photometric condition Note 1 to entry: The photometric condition should be specified (e.g. photopic, scotopic, mesopic). If it is not specified, photopic vision is assumed and the symbol K(λ) is used. For other photometric conditions, the respective symbol for identification shall be used. Note 2 to entry: Spectral luminous efficacy for photopic vision is expressed by K(λ) = Km V(λ) where Km is maximum luminous efficacy, V(λ) is spectral luminous efficiency and λ is wavelength. Note 3 to entry: The spectral luminous efficacy is expressed in lumen per watt (lm·W−1).
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