The acute non-image forming (NIF) effects of daytime light on momentary mood had been-although not always-established in the current literature. It still remains largely unknown whether short-time light exposure would modulate emotion perception in healthy adults. The current study (N = 48) was conducted to explore the effects of illuminance (100 lx vs. 1000 lx at eye level) and correlated color temperature (CCT, 2700 K vs. 6500 K) on explicit and implicit emotion perception that was assessed with emotional face judgment task and emotional oddball task respectively. Results showed that lower CCT significantly decreased negative response bias in the face judgment task, with labeling ambiguous faces less fearful under 2700 K vs. 6500 K condition. Moreover, participants responded slightly faster for emotional pictures under 6500 K vs. 2700 K condition, but no significant effect of illuminance or CCT on negativity bias was revealed in the emotional oddball task. These findings highlighted the differential role of illuminance and CCT in regulating instant emotion perception and suggested a task-dependent moderation of light spectrum on negativity bias.

Ambient illuminance and screen luminance have a significant influence on the visual fatigue and visual performance associated with the use of computers. The current study was conducted to investigate optimal screen luminance under different ambient illuminances and fit a curve of the optimum luminance of LCD screens under evening illumination. Thirty-three participants were assigned to rate screen brightness, visual comfort with screen luminance, satisfaction with ambient illuminance and visual fatigue under six screen luminance levels (3.87, 21.47, 42.74, 64.12, 84.77 and 106.7 cd/m²) combined with five ambient illuminance levels (0, 25, 50, 75 and 100 lx) in the evening. The results showed that optimum LCD screen luminance increased with increasing ambient illuminance. Moreover, ambient illuminance and screen luminance levels should be in the range of 13.08–62.16 lx and 20.63–75.15 cd/m², respectively, to obtain the optimal subjective feelings of visual fatigue and visual comfort during the evening.