RESEARCH ON PLEASANT DARKNESS IN A RESTAURANT

Abstract

Along with the development of lighting engineering during the high-growth period of the Japanese economy, the idea of "the brighter, the better" has become the paradigm. Darkness has been an essential part of Japanese architecture, to reveal its soft lighting distribution and to show expressions of texture being used. Several studies on darkness have been carried out to show the evaluation items, and shown that pleasant darkness depends on behaviors and lighting methods. Yet, these studies do not clarify the quantitative lighting environment range of pleasant darkness. Therefore, this research aims to show the pleasant darkness range depending on the lighting method and behavior of the room. Most standards use illuminance; yet, most designers agree that illuminance is not enough for designing, and researchers point out that luminance is more related to brightness of space. Therefore, within this research, lighting environment is defined not only by illuminance levels, but also with luminance distributions and several indices derived from them. The preliminary survey was conducted to define the target usage for the experiment. From the result of brain storming of "dark space", and pleasantness evaluation of it, a restaurant was set to be the target of this experiment. As a result of further literature survey of architectural magazines, three most popular lighting methods were selected to be the experimental setting. 1. Using spot light to lighten the table top, 2. uniformal light with down light and 3. spot light for table and indirect light for lightening walls. The first experiment was undertaken to select the most suitable experimental method and to verify the range of darkness. Experimental apparatuses were set as follows: square room with the white interior, a square table with food models, one spot light lightening the table top, and each participant eating with a mannequin as an accompanying person. 20 subjects were asked about the lighting environment using the adjustment method and the constant method. As a result, the existence of pleasant and dark lighting environments was shown using both experimental methods. The pleasant darkness range derived from constant method were between 120 to 151 lx and that of adjustment method were between 133 to 159 lx. For shortening experimental time and getting the precise threshold value, the experimental method of the second experiment was set to be the adjustment method. The second experimental was performed to see the relationship between the pleasant darkness and the lighting method and assumed behaviors. Three lighting methods and four behaviors (eating, drinking, chatting and relaxing) were set, and 20 subjects were asked to adjust until they reached the threshold value of darkness with ascending and descending series. The same procedure was taken for the pleasantness value. Using the logistic analysis, the pleasant darkness range were derived. ANOVA showed that the darkness threshold value and the pleasantness threshold value differed, and that these results were valid. The average luminance range was 5 ~ 17 cd/m2. According to the main visual target, the most-fit lighting environmental index differs. Experimental values were compared with the standards. The experimental results shows that subjects felt pleasant even if the average illuminance level is lower than the standard level. On the other hand, AIJES suggests the usage of average luminance of the interior surfaces. The experimental results showed that pleasant luminance level differs by the lighting method being used. Further investigations using different interior materials and different levels of brightness is needed.