Human perception and preferences of evening office lighting in terms of the LED spectrum

In pace with the development of modern society, the time people spent in the office has extended. This experiment explored human perception and preferences of evening office lighting. Two kinds of LED with three color temperatures were selected: ordinary LED and high color rendering LED, under 2700K,4000K, and 5000K. Ten subjects completed the evaluation of mood, preference, and color appearance in 6 environments (3 CCT *2 spectra). By analyzing people's ratings under the real-office environment, we found that high CCT generally improved subjects' positive ratings with the lighting environment but also will increase the tense level, while Ra didn't show significant influence.