## 6 Examination of a Real Lighting Scene  
We measured luminance distribution of a road in Shenzhen using a typical phosphor converted LED type. The road is 140 m in length and 16 m in width, as shown in Figure 9. We used a spectral image radiance colorimeter EVERFINE SIRC-2000 to measure the luminance distributions and spectral information of light sources. The colorimeter was set at 60 m far away and 1.5 m in height in each measurement. The luminaire was measured at a CCT of 3650 K, and the _S/P_ ratio in the 2- and 10-degree SSCs were 1.33 and 1.28, respectively. The average luminance was approximately 1 cd/m\({}^{2}\). The referred paradigm was a typical road lighting application at moderate CCT and luminance levels. We transformed the photopic adaptation luminance to mesopic luminance in a point-by-point manner. Figure 10 shows the luminance and the corrected mesopic luminance distributions. There are 810 luminance points in the road, which form the luminance distribution contours. The difference  
Figure 8: Mesopic luminance ratio using 10- and 2-degree SSCs as a function of CCT and photopic adaptation luminance. Figure 7: \(R_{gp}\) variations for CCTs in the range from 10000 to 45000K and ratio of \(R_{sps}\) in 10- and 2-degree SSC systems as a function of CCT. reasonable. We analysed the difference between these two SSCs based on an investigation of more than 300 light sources and extremely high CCT BR sources. Comparison of the _S/P_ ratios calculated using monochromatic light sources yielded considerable differences in the short-wavelength region (\(<\)500 nm). Light sources operating at high CCT values will likely cause considerable differences. In the very short-wavelength range (\(<\)430 nm), the S/P ratio increased abruptly. However, human eyes are not sensitive to changes in this region, and the precision of SSCs cannot guarantee the precision of the extremely high _S/P_ ratio. In the mesopic vision range, the differences in the mesopic luminance values of the 300 light sources calculated with the two SSCs increased as the photopic adaptation luminance values increased. In the scotopic vision cases, the same SSC \(V(\lambda)\) was applied and there were no differences. In photonic vision cases, the average difference reached a value of \(\sim\)6%. For some practical road lighting applications with luminance values less than 1 cd/m\({}^{2}\) and with moderate CCTs at approximately 4000 K, the difference of the corrected mesopic luminance values based on the two different SSCs studied herein was approximately 3%. For high CCT values (\(>\)6000 K), light sources, and high luminance levels (\(>\)1 cd/m\({}^{2}\)), the difference may reach 5%. Accordingly, as the differences of the two SSCs increase, the CCTs of the light sources also increased. The differences were relatively small and with values \(<\)5% for light sources operating with CCTs in the range from 2000 to 8000 K. For CCTs \(>\) 10000 K, the error at some mesopic luminance levels reached values \(>\)10%. In some research work, CCT light sources with extremely high _S/P_ ratios have been reported. The _S/P_ ratios for these light sources calculated using the two SSCs are so different that they require further analyses. For some special applications, like dashboard illumination in driving cabins and landscape lightings, blue LEDs might be used. Accordingly, considerable differences may be evoked. However, a few light sources applied in functional lighting operate at extremely high CCTs. Generally, the average difference of the _S/P_ ratio is approximately 8% for light sources operating at CCTs in the range from 2000 to 8000 K. The mesopic luminance values, which are related to both the photopic adaptation luminance and CCT, do not yield considerable _S/P_ ratio differences. For functional lighting, the photopic adaptation luminance is the main reason for the evoked differences. In summary, several valuable inferences were drawn based on the findings of this study.