This study examined how different lighting characteristics of conventional and eco-friendly lighting and environmental conditions, particularly snow cover, influenced the luminous environment and, in relation to that, pedestrian perception of faces on footpaths. The analysis was based on a dataset comprising both subjective evaluations and objective measurements. The spatial and directional light field above a footpath was measured for the two types of road lighting, of which the “eco-centric” luminaire had a lumen output of 4820 lm and reduced blue-light component (correlated color temperature (CCT) of 2200 K) compared to the conventional luminaire with 14,000 lm and 4000 K. The luminaires were analyzed under snowy and non-snowy conditions. Snow cover significantly increased light diffuseness and density (directionally averaged illuminance at a point), resulting in more uniform light and higher subjective ratings. Also, face visibility ratings were generally higher and more uniform, while non-snowy conditions led to more pronounced differences between positions and luminaire types. Regression analysis revealed that vertical illuminance at eye height was the strongest predictor of perceived facial friendliness and well-lighted-ness and contributed to more favorable ratings for the environment lighting too. The eco-centric luminaire was found to positively influence face lighting ratings but received lower ratings for environmental visibility. Increased horizontal illuminance did not consistently result in enhanced subjective evaluations, which points to limitations of traditional illuminance-based lighting standards, often considering horizontal illuminance at ground level as one of the main metrics. The “social light field” concept emphasizes a holistic approach to urban lighting design that integrates social perception and environmental sustainability by considering the distribution of the actual, resulting light throughout the urban space, especially vertical illuminance at the face and its effects on visual appearance, as well as contributing interactions with the environment and materials in it.

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”.