The discovery of a third photoreceptor in the human eye has shown that both, Non-Image-Forming (NIF) and image-forming effects of light, require attention in lighting design. Laboratory experiments have indicated that the direction at which light enters the human eyes may play a significant role in the magnitude of the NIF light effects due to either a non-homogenous distribution of the NIF photoreceptors across the retina or varying sensitivities of these photoreceptors.

A new method is proposed in which different retinal areas and their NIF effect’s contributions are included in analysis of luminous environments. The method is implemented to assess the influence of different façade arrangements and view directions on the magnitude of NIF effects of light. The findings show a high influence of both view direction and window size on the relative luminance values received from different areas in the visual field. A hypothetical weighting factor was introduced to account for NIF-related differences in sensitivity of the different retinal areas.