Discomfort Glare from Small, High-Luminance Light Sources When Viewed against a Dark Surround

ABSTRACT

This research examined human subjective responses to small, high-luminance light sources against low-luminance backgrounds and evaluated performance of four discomfort glare models. Forty-seven observers evaluated 36 conditions including three glare source luminances (20,000, 205,000, 750,000 cd/m²), two source positions (0°, 10°), two source sizes (10⁻⁵, 10⁻⁴ sr), and three background luminances (0.03, 0.3, 1 cd/m²) on a seven-point rating scale of perceived glare. The Unified Glare Rating (UGR) small source extension had the highest correlation with subjective responses (r = 0.879, P < 0.0001) within the ranges of the variables tested. This study validates and extends the UGR small source extension, typically used in interior spaces, to dark surrounds (for example, outdoor nighttime environments).

KEYWORDS:

• Discomfort glare
• glare model comparison
• LEDs and dark backgrounds
• psychophysical experiment
• UGR small source extension

Acknowledgments

The authors express their sincere gratitude to Musco Sports Lighting, LLC, in particular, Joe Crookham, Myron Gordin, Jeanie Bieri, Brad Schlesselman, Tim Barker, Lance Livingston, and Kevin Marshall. The authors also thank Dr. Carey Ryan for help with the statistical analysis.

Disclosure statement

The authors report no declarations of interest.

Additional information

Funding

This study was supported by Musco Sports Lighting, LLC through a sponsored research agreement entitled “Discomfort Glare in Outdoor Nighttime Environments” with the University of Nebraska–Lincoln.