Interpersonal judgements, lamp spectrum and task difficulty

The aim of this work is to identify optimum parameters for design of lighting for pedestrians to meet their needs for interpersonal judgements, including luminance and SPD. This paper discusses three factors that affect performance of a facial recognition task – the duration and distance of observation and the task carried out – as these factors affect the interpretation of the optimum luminance and whether or not the effect of lamp spectrum is significant. For SPD, it appears that this matters if the task is difficult (e.g. limited observation duration): a better SPD (for which the best parameter still needs to be defined) allows recognition at greater distances. For luminance, this might be defined by the knee in the plateau escarpment relationship. A new study is presented that suggests a relationship between task difficulty and facial recognition probability where task difficulty is defined as the product of observation duration and luminance.