The purpose of this study is to clarify the relation between subjective evaluation and luminous environment by arrangements of small electric light and colors of light source in daytime and nighttime. A subjective experiment was carried out using a mockup living room with a window surrounded by the artificial sky dome which can simulate the overcast sky. The result was shown as follows. 1) Small electric lights were not very needed under high artificial sky brightness condition, at least 1100cd/m2. 2) Location of lights on the ceiling influences the visibility under low artificial sky brightness condition, 100cd/m2. On the contrary, difference between a wall luminaire and a downlight does not influence the visibility. In addition, the arrangement of small electric lights improves the lighting quality and reduces electricity consumption for lighting. 3) Warm white color (2800K) light from the small electric light is more popular than the neutral white color (5000K) light under low artificial sky brightness, 330cd/m2.
