Color rendering and favorable color appearance

The appearance of colors (color rendering) differs in accordance with the spectral distribution of the light source. One method of quantitatively evaluating the color rendering of a light source is the method of evaluating the fidelity of the color appearance. This method quantitatively evaluates how well a particular lamp reproduces an object’s color compared to a reference light source. As stated above, this can be expressed as a color rendering index (CRI) numerical value. Furthermore, in addition to evaluating the fidelity of the color appearance, research on the method of evaluating the perceived pleasantness of colors has recently gained recognition. This method quantitatively evaluates whether shifts in color produced by a particular lamp compared to a reference lamp are in a favorable (perceived as pleasant) direction or an unfavorable (perceived as unpleasant) direction. Although evaluating the perceived pleasantness of colors is an important color rendering characteristic of light sources, no standardized evaluation method has been prescribed thus far, and so it can be considered an important research topic moving forward.