Abstract
Despite the fact that a 2-degree spectral sensitivity curve (SSC) is extensively used in scientific research and relevant applications, the choice between the 10-degree or the 2-degree photopic SSCs in practical applications for the calculation of scotopic/photopic ratios (S/P ratios) depends on actual needs. We examined S/P ratios for more than 300 light sources for correlated colour temperatures (CCTs) from 2000 K to 8000 K and blackbody radiant spectra from 10000 K to 45000 K using 2- and 10-degree SSCs. Results showed that the ratio of the S/P values calculated using the 10-degree and 2-degree SSCs was approximately equal to 0.916. The average mesopic luminance difference increased from 0% to 5.7% at a photopic adaptation luminance from 0.005 to 5 cd/m2. For most practical applications, the mesopic luminance values calculated using these two SSCs were different by several percentage units, yet these differences could be neglected. At extremely high CCTs over 10000 K, the mesopic luminance difference may approximate the maximum value of 16%. This work proposes the conversion coefficients for S/P ratios and the transforming mesopic luminance values calculated for 2- and 10-degree SSC systems. These results may help researchers clarify differences between the S/P ratios calculated using different SSCs.
Highlights
There are three vision states for human beings, photopic vision with luminance values >5 cd/m2, mesopic vision with luminance values from 0.005 to 5 cd/m2, and scotopic vision with luminance values
We examined the differences of the calculated S/P ratios with two sensitivity curve (SSC) based on tests with more than 300 light sources [23] with correlated colour temperatures (CCTs) from 2000 K to 8000 K, and with blackbody radiant (BR) light sources with CCTs from 10000 K to 45000 K
We analysed the difference between these two SSCs based on an investigation of more
Summary
There are three vision states for human beings, photopic vision with luminance values >5 cd/m2 , mesopic vision with luminance values from 0.005 to 5 cd/m2 , and scotopic vision with luminance values
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