Investigation of the daylight spectrum in an indoor environment using CIE S 026 melanopic metrics

Abstract

Since discovering the intrinsically photosensitive retinal ganglion cells (ipRGCs) and their impact on the circadian rhythm, many disciplines have been researching the physiological and psychological effects of light on humans. However, not much research has been conducted on how the spatial configuration of a room (orientation and gaze direction) changes the light quality and quantity. This research examines the variability of the natural lighting spectrum, focusing on light intensity, the spectrum itself, as well as variations across seasons and hours. The metrics examined are the CIE S 026 melanopic equivalent daylight illuminance (melanopic EDI) and melanopic daylight efficacy ratio (melanopic DER). Field measurements were taken in a room with a south orientation located in Cyprus, using a spectrometer. The main parameters under study were eight gaze directions, four seasons (June, September, December and March) and four different hours each day (09:00, 12:00, 15:00 and 18:00) for 20 positions in the test room. The results show the impact of season, time and gaze direction on the melanopic DER and melanopic EDI. Overall, due to the low sun angle and direct sunlight exposure in the winter, the melanopic EDI was much higher compared to the other three seasons, whereas the melanopic DER had the lowest values. For all seasons and times, most of the cases achieved the minimum recommendation for daytime light exposure of melanopic EDI of more than 250 lx.

Electrochromic Glazing and Evaluation of Visual and Non-Visual Effects of Daylight: Simulation Studies for Brasilia – Brazil

“…Melanopic daylight efficacy ratio (mel-DER) is the ratio of a test source's melanopic efficacy of luminous radiation to the melanopic efficacy of luminous radiation of CIE Standard Daylight D65. Melanopic DER is unitless, with the value 1 corresponding to the light source of D65 [45,70]. In the simulated room, mel-DER was calculated considering the two solstices and the two equinoxes from 8:00 a.m. to 6 p.m., totalizing 40 hours for each solar orientation, north, east, south, and west for each sensor, P1 to P9.…”

Editorial: Special issue for early career researchers in lighting

“…Focusing on the NIF effects of lighting, Gkaintatzi-Masouti et al 5 reviewed existing tools to simulate non-image forming effects of light and pointed out the lack of models to describe personal light history and gaze direction, as well as the lack of data to characterise sky spectral information. Relating to the importance of gaze direction, Englezou et al 6 examined the variation in CIE S 026 melanopic metrics across different gaze directions, seasons, and hours through field measurements in a daylit south-facing room in Cyprus.…”