Influence of Spectral Power Distribution on Scene Brightness at Different Light Levels

ABSTRACT

Exterior lighting has multiple objectives. Brightness perception is a relevant parameter for outdoor lighting because it is correlated with perceptions of safety and security. Understanding the influence of the spectral characteristics of lighting to scene brightness perception is important in order to devise exterior lighting specifications that support perceptions of safety and security in exterior lighted environments, as well as to optimize light source technologies to account for these factors. A study of scene brightness perception under different light levels and spectral power distributions was conducted to assess whether scene brightness perception exhibited increased short-wavelength spectral sensitivity as a function of increasing light level. The results confirm that a successful model of spectral sensitivity for scene brightness perception should incorporate a shift in short-wavelength sensitivity like the one investigated in the present study.

• brightness
• exterior lighting
• mesopic photometry
• SPD
• spectral sensitivity

ACKNOWLEDGMENTS

This study was supported by the Jim H. McClung Lighting Research Foundation. Diarmuid McSweeney served as project manager, and helpful guidance was provided by Terry McGowan. Jean Paul Freyssinier, Mariana Figueiro and Robert Hamner from the Lighting Research Center provided valuable technical input. The authors are also grateful to the experimental subjects who patiently participated in the studies described in the present article.