The effect of correlated colour temperature and wall luminance on spatial brightness and scene preference in a windowless office setup
Laurens Van de Perre, Kevin Smet, Peter Hanselaer, Marc Dujardin, Wouter Ryckaert
Abstract
This study explores the impact of wall luminance and correlated colour temperature (CCT) on the observers’ brightness perception and scene preference in a controlled, windowless office environment. A two-interval-forced-choice experiment was conducted with the 20 lighting scenes derived from five CCTs (2500–10 000 K) and four luminances (12–120 cd/m²). The results from 20 observers showed that a higher wall luminance significantly increased brightness. At equal luminances, different CCT values had no significant effect on brightness, consistent with some reports that CCT is not a reliable predictor of brightness when other photometric factors are held constant. Scene preference increased as wall luminance increased to approximately 72 cd/m², but a further increase in wall luminance to 120 cd/m² had no significant impact on preference. As the CCT increased from 2500 K, the preference increased up to approximately 4000 K, followed by a substantial decline from 5715 to 10 000 K.