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The relationship between lamp color characteristics and brightness perception is not well known. In this study, nine lighting environment with correlated color temperature (3000 K, 5000 K, and 8000 K) and illuminance (1000 lx, 300 lx, and 100 lx) were created. Both the side by side visual matching and spatial brightness scaling experiments are designed to verify the effects of correlated color temperature on spatial brightness perception. The results of the study show that lighting with high correlated color temperature will have stronger spatial brightness perception than lower ones.

Several models on the circadian effect have been applied to indoor circadian lighting design, but applications in road lighting have not yet been clarified. Based on existing models and circadian research, we examined equivalent melanopic lux (EML), circadian light (CLA), and circadian stimulus (CS) representing the circadian effect and the S/P ratio representing the mesopic vision effect, among a dataset of light sources at photopic adaptation illuminance values of 1, 3, 10, 30, and 100 lx. The results show that the S/P ratio correlates with EML and CS (or CLA) much stronger than it correlates with color temperature. The EMLs of light sources are below 50 EML in mesopic vision, and the CSs of most light sources are below or around the threshold value of 0.05. We conclude that the circadian effect is not a significant issue in mesopic vision under most conditions and that optimization for mesopic efficiency is still a good strategy. There are quite a few light sources that may achieve both ideal mesopic efficiency and low CS. This work clarifies the circadian effect and mesopic vision effect performance of light sources in mesopic vision and will help guide choosing suitable light sources and optimization strategies for road lighting.

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