Dr. Robert Davis Profile

Dr. Robert Davis

at Pacific Northwest National Lab

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Proceedings Article | 8 March 2021 Presentation + Paper

Examining perceptual luminance uniformity of simulated luminaire patterns

Belal Abboushi, Eduardo Rodriguez-Feo Bermudez, Lia Irvin, Benjamin Feagin, Michael Royer, Robert Davis

Proceedings Volume 11706, 117061E (2021) https://doi.org/10.1117/12.2577901

KEYWORDS: Light sources and illumination, Visualization, Visual system, Spatial frequencies, Contrast sensitivity, Buildings

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Luminaire luminance uniformity is an important aspect that can affect perceived lighting quality, discomfort glare, and efficacy. While several metrics have been proposed to characterize luminance uniformity, previous studies have shown that current metrics such as Max:Min or Avg:Min luminance ratios can be insensitive to important differences in luminance gradient that may affect perceived uniformity. In an attempt to resolve this issue, previous studies incorporated a contrast sensitivity function for the human eye based on spatial frequency, such as in the recently proposed UHVS metric; however, this metric has not been comprehensively studied in relation to perceived uniformity ratings. The study presented in this paper aimed to examine the relationship between UHVS and perceived uniformity ratings. Specifically, simulated luminance patterns were presented, and participants were asked to assess uniformity using a twoalternative forced-choice procedure. The results of 94 participants’ evaluations showed a significant correlation between UHVS and perceived uniformity. However, comparisons between patterns that had similar UHVS sometimes resulted in statistically different ratings and comparisons between patterns that had larger differences in UHVS sometimes did not result in a statistically significant difference in ratings. These results suggest that UHVS might be used for general guidance but may warrant further studies to better understand its sensitivity and improve its alignment with perceived uniformity ratings.

Proceedings Article | 5 March 2021 Poster + Presentation + Paper

The effect of spectral resolution of light sources on photopic and α-opic quantities

Belal Abboushi, Sarah Safranek, Robert Davis

Proceedings Volume 11706, 117061L (2021) https://doi.org/10.1117/12.2577934

KEYWORDS: Spectral resolution, Light emitting diodes, Light sources, Light sources and illumination, RGB color model, Light, Databases, Computer simulations

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There is a growing interest in including light source spectrum in advanced lighting software tools and simulations. Given that traditional lighting software tools have been used primarily for calculating photometric quantities, their simplifying assumptions may not be suitable for calculating other α-opic quantities. Commonly used simulation tools use three values to represent the three primary colors (red, green, and blue), but others have expanded the number of bands (i.e., the spectral resolution) to 9, 27, or 81 in an attempt to more accurately represent variations in light source spectrum and downstream spectrally-derived quantities. It remains unclear, however, to what extent spectral resolution affects calculated quantities. To address this gap, a numerical analysis was completed using a large spectral power distribution database (n = 1,302 light sources). Calculated illuminance, α-opic irradiance, luminous efficacy of radiation (LER), melanopic efficacy of radiation (MER), and melanopic to photopic (M/P) ratio were compared for spectral resolutions of 3 and 9 bands compared to a baseline of 81 bands. Across all examined lighting quantities, considerable errors—a mean absolute percent error of 19%— were found when using 3 band calculations. These were reduced to 4% for 9 band calculations. The errors varied by metric and light source type. The results suggest that the use of 9 bands can more accurately characterize performance of different light source types across a range of metrics compared to using 3 bands.

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