An index for quantitative evaluation of the color discrimination property of sunglass lenses was calculated as the ratio of the color gamut area formed by the eight CIE-1974 test-color samples for the general color rendering index on the CIECAM02 colorfulness plane under the standard illuminant D65 after passing through the sunglass lenses under test to the gamut area formed by the samples on the plane under the illuminant D65. The index was validated by a very high simple correlation coefficient between the visual evaluation results and the indices of the color discrimination property. Furthermore, it was shown that blocking the spectral component around 565 nm effectively improves the color discrimination property and that a spectral transmittance factor that blocks wavelength components in a 500-nm area effectively improves color discrimination and enhances colorfulness for the color yellow simultaneously.

The purpose of this research was to create a lighting environment that enhances the beauty of the natural landscape of a resort area with a wealth of nature. Lighting with a low color temperature and low illuminance was used. Though snow coverage was taken into consideration, light fixtures were positioned as low as possible. In addition, highlighting essential elements in the landscape was considered. Although the average illuminance was less than half of what it was before, the number of difficult places to walk decreased significantly, and there were more spots in which to take photographs. A possibility that low-illuminance outdoor lighting could also affect a person’s sense of hearing in the natural surroundings was pointed out.