Perceived adequacy of illumination, spatial brightness, horizontal illuminance and mean room surface exitance in a small office

This paper presents a pilot study that investigated the suitability of mean room surface exitance as a predictor of spatial brightness and perceived adequacy of illumination, and then compared these results with how horizontal illuminance predicted both items under the same conditions. The experiment included 26 participants. A small office was used for the study. It exposed participants to three levels of mean room surface exitance, each delivered with three different light distributions and across three different surface reflectances, resulting in a total of 27 light scenes. A clear relationship existed between mean room surface exitance and both perceived adequacy of illumination and spatial brightness, but not between horizontal illuminance and either item. Correlations were drawn between reported levels of spatial brightness and reported levels of perceived adequacy of illumination.