UCL Institute for Environmental Design and Engineering


Chengpeng Zhao

Modelling human evaluations of daylight and electrical lighting with various SPDs

Although our understanding of effects of light on health and wellbeing has developed rapidly, we are still a long distance away from achieving a comprehensive understanding of the implications to allow easy implementation of this knowledge in practice. For example, a large number of experiments have been conducted to separately investigate the impacts of spectral power distributions (SPD) of light on the human’s circadian system and impressions of interior lighting. However, it is still not clear how to simultaneously balance the physiological benefits of light on circadian entrainment and user acceptance/preference of interior lighting.

The aim of this study is to explore the influences of SPD on visual perceptions and mood (affects) in the context of what is now commonly termed Human Centric Lighting (HCL). The specific objectives in addition to colour rendition, are to determine the role of daylight as reference light source for human evaluation on electrical light sources with CCT > 5000K. Secondly, to investigate the correlations between objective colorimetric properties and subjective human impressions. Thirdly, to seek a balance between the non-visual Melanopic effects and user preference of cold white lighting. Psychological experiments will be conducted with multi-channel LED sources which are able to closely resemble the SPD of daylight. Perceived naturalness, preference and mood (affects) will be measured in addition to visual perceptions.

Raising understanding of the effects of SPDs, may help the lighting designers and manufacturers to choose the optimal light spectra for occupants’ health and wellbeing.