Effects of correlated color temperature of office light on subjective perception, mood and task performance

Research has shown multiple effects of light correlated color temperature (CCT) on office staff. However, the CCT ranges in previous research were relatively narrow. This study investigated the effects of CCT over a wider range and examined the influence of task type and light exposure duration. A within-subject design involving 4 CCTs (4000, 6000, 8000, and 10,000 K) × 2 task types (computer vs. paper-based task) × 2 test times (5 vs. 90 min) was employed. The results showed that CCT had main effects on perception, mood, and performance. Participants felt more comfortable but also sleepier under the lighting of 4000 K than other CCTs. Positive mood deteriorated, but task performance might improve with a gradual CCT manipulation from 4000 K to 10,000 K. Furthermore, participants rated their mood more positively with computer tasks than with paper-based tasks, but no significant effect of light exposure duration was found in this study. These findings highlight that the optimal CCT level varies for different demands such as comfort, positive mood, alertness and task performance, so selection of office light CCT should be weighed according to the scenario demands. •Effects of office light CCTs were investigated for a wide range of 4000–10000 K.•The influence of task type and light exposure duration were analyzed.•The optimal CCT level varied for comfort, mood, alertness, and performance.•Results showed a more positive mood with computer tasks than paper-based tasks.