No abstract

No abstract

Luminance distributions would be very suitable as input for lighting control systems that aim for a comfortable lit indoor environment. Luminance distribution measurements should then correspond to the visual field of the user. However, this will interfere with office activities. Therefore, this study aims to validate whether it is feasible to approximate the luminous conditions experienced by the user using ceiling-based measurements instead. The average desktop luminance was measured using a luminance camera, under varying conditions, simultaneously from eye level and ceiling and their relations were analysed. Normalized root mean square errors were found ranging from 10,3 % to 14,3 %, while the average bias was 14,2 % between measurements from eye level and ceiling. Based on these results, it is concluded that the experienced desktop luminance cannot be exactly replicated by ceilingbased measurements. However, ceiling-based luminance measurements are able to provide a reasonable approximation that suffices for practical systems.

Presently, luminance distribution measurement devices, using High Dynamic Range technology, are increasingly used as they provide a lot of relevant data related to the lit environment at once. However, the accuracy of these devices can be a concern. It is expected that the accuracy would be improved by incorporating the effect of the camera spectral responsivity and the spectral power distribution of the illuminant under which the measurements are conducted. This study introduces two optimization criteria incorporating these aspects to improve the spectral match and the performance of luminance distribution measurement devices. Both criteria are tested in a theoretical model and in practical measurements using two cameras and three illuminants: LED, halogen and fluorescent. Both methodologies support the hypothesis that the conventional method to determine the luminance introduces spectral mismatches that can be limited by optimizing relative to the spectral responsivity of the camera. Additionally, substantial evidence was found, by both the theoretical model and the validation measurements, that the spectral power distribution of the illuminant also has an effect on the performance.

No abstract