Perceived room brightness: Pilot study on the effect of luminance distribution

This paper describes an experiment to investigate the influence of luminance distribution on perceived brightness in interiors. Thirty subjects matched the brightness of mock offices using a dimmer. Two of the four mock offices used in the experiment had relatively uniform luminance distributions, created by ceiling fluorescent lighting equipped with K-12 acrylic lenses. The other two offices had a nonuniform luminance distribution created by substituting parabolic louvres for the acrylic lenses. In control comparisons subjects matched two rooms having the same luminance distribution. In experimental comparisons subjects matched two rooms having different luminance distributions. The rooms with the nonuniform luminance distribution required between five and ten percent less working plane illuminance to match the brightness of the rooms with the uniform luminance distribution. This raises the possibility of modest energy savings through lighting design.