The freedom of light characteristics in atmosphere perception for the living room

With the introduction of LED lighting, nowadays designers and architects have more flexibility to evoke emotions and create certain atmospheres in a space by means of artificial lighting. The perceived atmosphere in a space is an experience of the surroundings in relation to ourselves; it is an affective evaluation of the environment (Scholten et al., 2003; Vogels, 2008). Previous studies related to atmosphere perception have given valuable insight into the relation between white light and the perceived atmosphere (Vogels et al., 2008). Moreover, in (Seuntiens and Vogels, 2008) four atmospheres (cosy, relaxing, activating and exciting) were designed by professional lighting designer for a standard living room and verified by end users. This study found clear commonalities between the professional lighting designers with respect to the chosen light characteristics to evoke a certain atmosphere in the room. However, it was not clear how much variation in light characteristics was allowed before an initially perceived atmosphere disappears. In the present research three experiments were conducted to investigate the allowed variation in light characteristics (luminance, color temperature, hue and saturation) on two atmospheres, namely cosy and activating. In the first study, a tuning experiment was conducted in order to investigate the allowed variation in light characteristics on the initially perceived “cosy” and “activating” atmosphere. In general, the results of the first experiment showed that participants allowed quite some variation in light characteristics in both atmospheres. On average participants allowed an increase in luminance of the white light sources of a factor two to four compared to the initial luminance level, and a decrease in luminance of at least a factor of two. Furthermore, a consistent change of about 800K was allowed for the increase in color temperature in the “cosy” atmosphere and the decrease in color temperature in the “activating” atmosphere. Due to technical limitations, the decrease in color temperature in the “cosy” atmosphere and the increase in color temperature in the “activating” atmosphere were not investigated in this study. Finally, the allowed change in hue and chroma of the colored luminaires was found to be larger in the “activating” atmosphere than in the “cosy” atmosphere. In order to investigate the effect of a change in light characteristics on the perceived atmosphere, a difference scaling experiment was conducted. In this experiment, participants compared the average allowed change in light settings as obtained from the first study to the light settings corresponding to a “cosy” or “activating” atmosphere as reference. A short version of the original atmosphere questionnaire of Vogels (2008) was used to assess the perceived atmosphere in the room. The results showed that an increase in luminance of the white light sources reduced the cosiness and tenseness of the atmosphere, and enlarged its liveliness and detachment (with a reverse effect for a decrease in luminance). A decrease in color temperature was found to increase the cosiness, and to reduce the liveliness and detachment of the atmosphere. With regard to the colored luminaires, a change in hue was found to mainly affect the cosiness and detachment, whereas a decrease in chroma mainly affected the liveliness and detachment. In a follow-up experiment participants assessed the perceived atmosphere for the allowed change in light settings without the initial “cosy” and “activating” atmosphere as a reference to compare with. In general, similar trends with respect to the changes in the atmosphere were found, however, the effects were considerably smaller. This indicates that participants found it more difficult to distinguish the atmosphere related to the different light settings when they could not directly compare them. In this study, boundaries for the allowed variation in luminance, color temperature, hue and chroma were obtained for the “cosy” and “activating” atmosphere. In addition, the results gave further insight into the relation between light and perceived atmosphere. However, this research also has its limitations in the sense that some light characteristics, such as the spatial distribution of the light, and its dynamics, as well as the spatial configuration of the light sources, were not included. More research is needed to investigate the effect of these aspects on perceived atmosphere further.Man-Machine Interaction GroupElectrical Engineering, Mathematics and Computer Scienc