Footpath Lighting: Optical, Visual, and Perceptual Characteristics of the Social Light Field

We studied how the characteristics of the light field, under varying real lighting conditions on footpaths at night, affect the appearance of a head-shaped light probe. A combination of physical light field measurements, image analysis, and a formal perception experiment using photographs was applied to understand how lighting characteristics affect the appearance of the face and environment. This empirical study was done in four different light configurations and for snowy and non-snowy conditions. We found that the resulting local light diffuseness, light vector, and vertical illumination correlated with the perception of friendliness, how well the faces were judged to be lit, and how comfortable the environment was rated. These local light qualities vary throughout the measured field, spatially and directionally, and showed a major effect of the presence of snow. This implies that managing and optimizing the actual light field characteristics or the spatially and directionally varying quality of the light in the three-dimensional space above the footpath is needed to fully capture its affordances such as walkability and its experiential values such as comfort in low light conditions. Extending architect Jan Gehl’s idea of the “Social field of vision”, to incorporate optical, visual, and perceptual aspects of human-centered lighting design, we propose the “The Social Light Field”.