Abstract
Brightness perception of object colors is affected by the change of color-rendering property of illuminating source, even though the illuminance is kept constant. The cause of this phenomenon is thoroughly studied by a thinking and a subjective experiment, specifically relating to the Kohiraush effect studied by Sanders (ref. 12, 13, 14) and Thornton (ref. 10, 11).
The subjective experiment was done for various object colors by using three kinds of fluorescent lamps with the general color-rendering indies Ra of 64, 84, and 87.
Results are summarized as follows.
(1) The brightness equation proposed by Thornton is inadequate.
(2) The effect of color rendering properties of lighting sources on brightness of object colors is larger than that predicted by the Kahlraush effect studied by Sanders.
(3) Brightness of object color is perceived to increase for an increase of its metric chroma by changing illuminating fluorescent lamps from low to high Ra value.
