“Visual clarity” is considered one of the most important characteistics of the color rendering properties of light sources, however, it cannot be adequately estimated by using the present CIE or JIS
Ra method. For this reason, we previously studied the cause of visual clarity and found that visual clarity was caused by the feeling of contrast between colored objects under illumination, and proposed a new index of the feeling of contrast for a light source that uses the non-linear color appearance model by Nayatani et al.
The purpose of the present study is to propose practical method for calculating and indexing the feeling of contrast for a light source that uses the CIELAB color space and CIE chromatic adaptation equation instead of the non-linear color appearance model by Nayatani et al. A new practical index of the feeling of contrast for a light source correlated well with one obtained using the non-linear color appearance model. Use of this proposed method with the CIE/JIS
Ra method will make it possible to estimate the color rendering properties of light sources more accurately.
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