Effect of indoor surfaces’ spectral reflectance on the environmental light spectrum modification and on objects perceived color

Abstract

In indoor lighting, the illuminance and spectral power distribution of the light incident on the contained objects, and hence the color rendering abilities, are not only due to light sources, but also to the indoor architectural surface's geometrical and lighting properties (e.g. spectral reflectance functions). This circumstance, for interior lighting designers, might be as relevant as the appropriate choice of light sources;Main purpose of the study is to highlight how coloured walls can affect indoor environmental light and modify objects perceived color; despite its importance, it is quite a neglected aspect, and has been little investigated, especially in comparison to a wide range of studies about users’ satisfaction with the correlated color temperature of the emitted light and the ability of such artificial light in rendering colors. To take into account spectral reflectance distribution of surfaces, a mathematic calculation model has been developed and implemented in Matlab. This paper evaluates, through numerical simulations, the relative importance of the two factors – light sources and properties of the walls-having influence on indoor lighting.A primary source with CIE D50 spectrum has been considered, and the effect of diffuse Lambertian reflection from the walls with different spectral reflectance functions, to evaluate the spectrum of the light incident on different tasks in the room, and the consequent impact on their color appearance have been studied. Influence of objects’ position has also been investigated. Resultsshow that this impact is remarkable, and are visually presented through a graphic coloured pictorial representation, giving evidence of how perceived colors of objects in an environment with coloured walls appear different from the case of white or grey walls, or of presence of direct light only. This result is highlighted also through the use of a Color rendition index that reaches, in some cases, values far from the optimum.