Research to better understand the tradeoffs between visual comfort and efficacy involves investigation of luminance uniformity perception when observing LED arrays behind various diffusing materials. This research is intended to evaluate the performance of existing and proposed metrics for assessing uniformity perception, identify tradeoffs between visual appearance and the efficiency of optical materials, and eventually lead to reduced energy use through the development and deployment of advanced luminaires.

Luminance Pattern Perception

An apparatus in Pacific Northwest National Laboratory’s Lighting Science & Technology Lab is designed to enable evaluation of variable luminance patterns from a mock luminaire, in conjunction with accurate measurement of the luminance. Prior to laboratory experiments, a virtual study was conducted to test existing measures of uniformity perception and probe hypotheses for continued research.

Examining Perceptual Luminance Uniformity of Simulated Luminaire Patterns (Journal Article, March 2021)
Apparatus for Studying Human Perception of Luminaire Luminance Uniformity (Conference Paper, August 2020)

As part of this research, procedures for using high dynamic range imaging (HDRI) for characterizing luminaires are being developed. A prior literature review identified four sources of significant error in HDRI and discussed their cause, magnitude, and available correction methods. The review also offered recommendations for minimizing possible errors in HDRI luminance measurements as well as topics for future research.

Developing High Dynamic Range Imaging Procedures for Luminance Uniformity Measurement (Conference Paper, August 2020)
Sources of Error in HDRI for Luminance Measurement: A Review of the Literature (Journal Article, March 2020).

Black-and-white image of a lens flare at left; same image at right, with direct light blocked from camera lens, showing only a white circle against a black background.

Example of HDRI image demonstrating lens flare (left) and the same scene with all direct light blocked from camera lens (right).