抄録
Lighting designers have long accepted Kruithof's proposal that warm lighting is preferred over low intensities of illumination, and cool lighting is preferred over high intensities of illumination. However, when considering these preferences in color temperatures, Kruithof's proposal does not take into account seasonal changes or differences in age. Kakitsuba et al. (2000a, 2000b, 2003) demonstrated a seasonal change in color temperatures preferred by young Japanese subjects aged between 19 and 27 under illumination intensities of 200 lx and 1,500 lx, and an age difference in preferred color temperatures when the results were compared with those obtained for eight Japanese female subjects aged between 36 and 45 under an illumination intensity of 1,500 lx. Following these studies, the same middle-aged female subjects were exposed to 3,000 K and 7,500 K in controlled room temperatures of 22°C and 30°C. The illumination intensity was set at 200 lx on each occasion. Following controlled exposure for 30 min. at 25°C in a darkened room, subjects were exposed to given lighting and thermal conditions. Skin and oral temperatures, ECGs and blood pressures were measured throughout the exposures. At 15 min. intervals the subjects reported on comfort, calmness, brightness and thermal sensations. The resulting changes in HF values indicated that the subjects preferred 7,500 K to 3,000 K. This demonstrated that Kruithof's proposal could be accepted for middle-aged female subjects in the case of 200 lx as well as 1,500 lx.
