Tetsuya Eda

Influence of surround luminance upon perceived blackness

In this study, we investigated how the luminance ratio of the surround field (Ls) to that of the central field (Lc) influence the perceived blackness of the central field in a simple configuration of concentric circle (Experiment 1) and in digital images of masterpieces (Experiment 2). Results of Experiment 1 showed that perceived blackness of the central field becomes more blackish and deeper as the contrast between Lc and Ls increases. Results of Experiment 2 showed that perceived blackness of black area surrounded by relatively bright area in artistic images is stronger than the perceived blackness given by the same luminance contrast between the center and surround in a concentric circular configuration.

Whiteness perception in Japanese and Finnish under cool and warm fluorescent lamps

In this study, we conducted the experiment to compare the whiteness perception of Finnish and Japanese observers. The rank order of perceived whiteness among seven nearly white Munsell chips (Value is 9.25 or 9.5, Chroma is 0, 0.5 or 1.0) under the fluorescent lamps of correlated color temperatures of 3000K, 5000K, and 6700K was determined. Observing condition employed in the two laboratories was exactly the same as well as the experimental procedure. In 3000K condition, the results of Japanese and Finnish observers agreed with each other quite well, while as the correlated color temperature becomes higher, the results from the two laboratories showed different tendencies. Negative correlation was found between the whiteness rank order and the metric chroma for all of the results.