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M/P Ratio Method – Simplified Field Measurement Method for CIE Mesopic Photometry System



Yoshihiro Ohno, Tatsukiyo Uchida


For the implementation of the mesopic photometry system in CIE 191:2010 to outdoor lighting, two simplified methods to measure the mesopic luminance in fields have been proposed. One of the methods, named M/P ratio method 1, assumes that the spectral distributions (SPDs) of test objects are the same as that of the adaptation field. Another method, named M/P ratio method 2, assumes that it is equal to the SPD of the light source. Error simulations with a real asphalt spectral reflectance library show that the variation of the asphalt spectral reflectance does not cause significant error with the methods. Although the bias by the pavement spectral reflectance to the SPD of the test objects causes large error with M/P ratio method 2, a proposed correction method can reduce the error sufficiently. Error simulations also show that M/P ratio method 2 is robust for lighting scenes that includes multiple type light sources. It has been shown that M/P ratio methods can measure the mesopic quantities without a scotopic/photopic instruments having both V(λ) and V′(λ) detectors.
Lighting Research & Technology


mesopic photometry, M/P ratio, field measurement


Ohno, Y. and Uchida, T. (2017), M/P Ratio Method – Simplified Field Measurement Method for CIE Mesopic Photometry System, Lighting Research & Technology (Accessed May 18, 2024)


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Created October 16, 2017, Updated January 8, 2018