COMPARING THREE SUBJECTIVE METHODS FOR ASSESSING DISCOMFORT GLARE

Title COMPARING THREE SUBJECTIVE METHODS FOR ASSESSING DISCOMFORT GLARE
Author, Co-Author Robert Jacobs, Mark Bullimore, Ian Bailey, Sam Berman
Topic
Year
1992
Day
Saturday
Program Number
1:30 pm
Room
Ireland B
Affiliation
Abstract Assessment of discomfort glare has practical and research implications for clinical and ergonomic purposes. We compared 3 different subjective methods for assessing glare discomfort. For all methods, the variable intensity glare source was a projector beam 2 deg in diameter located 11 deg to one side of a central tracking task. The glare source was presented in 2 second exposures 2 seconds apart. The first method required adjustment (ADJ) of the projector luminance by the subject until the glare was judged to be at the border of 'disturbing' discomfort. The second method was a 2- alternative forced choice (2AFC) procedure in which subjects judged whether the glare exceeded the border for 'disturbing' discomfort within a interleaved double staircase limited by ten reversals. For the third method, four different categories of discomfort - perceptible, noticeable, disturbing and intolerable - were described and subjects were presented with 6 glare intensities, each 6 times. Subjects indicated the degree of discomfort by marking a visual analog scale (VAS) on which the 4 categorical borders were marked. Within each of two sessions, trials with the three different methods were run twice in randomized orders to allow analysis of within-and between-session changes in response. For 18 young adult subjects, there was a very consistent pattern of results: The lowest luminance thresholds for disturbing discomfort were obtained by the ADJ and the highest for the VAS method. In a consistent trend, subjects showing most tolerance to glare (higher thresholds) showed quite similar thresholds for the three methods, while the least tolerant subjects showed about 2 log units difference between their ADJ and VAS thresholds for disturbing discomfort. Within sessions, particularly the first, subjects consistently developed lower thresholds for discomfort glare, and there was also a small between-session increase in glare sensitivity. The VAS method is the most r
Affiliation of Co-Authors
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