Abstract This study aims to propose a new integrative dimension, namely, Brilliantness, which lies between brightness and vividness in the practical color coordinate system （PCCS）. It also intends to investigate the relationship between color attribute and color impression. Hence, two experiments were conducted. Experiment 1, which focused on color impression, selected 24 stimuli （specifically, 11 tones, 12 hues, and an achromatic color） from the PCCS. These stimuli were assessed using 20 pairs of adjectives derived from the semantic differential technique. Experiment 2 considered 12 tones of stimuli and utilized the visual analog scale to evaluate color brightness and vividness. Subsequently, principal component analysis was performed to integrate color brightness and vividness into one dimension. The results revealed a significant contribution which was facilitating the definition of “Brilliantness.” A subsequent factor analysis identified four dimensions of color impression. Additionally, color brightness and vividness were found to be correlated to these dimensions of color impression, which were correlated with “Brilliantness.” Thus, the results demonstrated that “Brilliantness”facilitates the quantitative expression of color impression.

We proposed a novel method for estimating the cone fundamental functions, CFFs, of individual observers by metameric color matching experiments with non-monochromatic light stimuli on a general-purpose display and color filters. In the proposed method, CFF is defined by a physiologically valid visual model and estimated for color matching data with several reference stimuli using a differential evolution method. Simulation experiments were conducted using actual spectral data such as the spectral radiance of displays and the spectral transmittance of color filters to verify the effectiveness and validity of the method. From the results of the simulation experiments, we confirmed that CFFs can be estimated with accuracy by repeating metameric color matching using three or more color filters with different spectral transmittance and applying the differential evolution method to the average result. We also examined the relationship between matching fluctuations and estimation accuracy and confirmed the robustness of the estimation method in practical situations where variations in matchings occur depending on the color discrimination threshold of observers.

Color constancy between LED illuminants with different chromaticities and spectral distribution shapes was investigated. In the experiment, the color appearance of color charts was evaluated with Weight Category Evaluation method（WCE）under 12 different illuminants, combining 3 spectral distribution shapes and 4 chromaticities. The WCE scores were converted to the elementary color components of Elementary Color Naming method（ECN）and compared with the change in u'v' chromaticities. The results showed that the correspondence between the chromaticity change and the change in color appearance varied depending on the lighting conditions compared. In order to take the color adaptation into consideration, the relative chromaticity change to that of the back wall（an achromatic color）of the experimental booth was compared with the change in color appearance. The results showed a good correlation of the relative chromaticity change and the color appearance change regardless of the illuminant conditions. The change in whiteness and blackness components of ECN showed no obvious relationship with the luminance change because of the small luminance modulation due to the constant illuminance condition.

The function of color sense has a variation, but this idea is still not common in Japan. Therefore, students and pupils struggle during some school activities and lose confidence to communicate with others about a topic of colors. In this study, we aimed to identify the components of color vision diversity. We conducted a two-step study. Firstly, we reviewed articles and books written in the perspective of color vision diversity, and composed the elements quoted in the literature for three lists. Secondly, we interviewed three authors of the literature and confirmed the contents of the lists. Those researches revealed three components themes: a color-universal environment for school; empowerment for color-deficient students; extending the idea of the diversity of color vision and accurate knowledge about color, color sense, and color deficiency. We expect to use the results of this study to design an educational program for color-blind students and pupils, common color sense students and pupils, and teachers in school activities.