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The e-ILV provides free access to all the terms and definitions contained in the international standard CIE S 017:2020 ILV: International Lighting Vocabulary, 2nd edition.

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17-21-113

S/P ratio

RSP

ratio of the luminous output of a source evaluated according to the CIE scotopic spectral luminous efficiency, V'(λ), to the luminous output evaluated according to the CIE photopic spectral luminous efficiency, V(λ)

Note 1 to entry: The S/P ratio is expressed by

where ≈ 1 700 lm·W−1 is the maximum luminous efficacy for scotopic vision, Km ≈ 683 lm·W−1 is the maximum luminous efficacy for photopic vision, S(λ) is the relative spectral distribution of the source, and λ is the wavelength.

Note 2 to entry: The S/P ratio has unit one.

Publication date: 2020-12
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