Testing Experimental Methods for Discomfort Glare Investigations

Abstract

Discomfort glare has been investigated for more than a century using various experimental methods. Most of them were based on psychophysical procedures and few others relied on physiological measurements as indicators of it. In this paper, we compare some of these methods to determine the most relevant ones to investigate discomfort glare in an indoor environment. With the same experimental set-up, two experiments were led. In the first one, 35 subjects evaluated two glare sources with different spectral power distribution with seven different psychophysical procedures. In the second one, four physiological measurements were recorded for eight subjects while they were illuminated by the same light sources. Based on the repeatability, the limits and the potential biases of each procedure, three psychophysical methods are recommended to evaluate discomfort glare at photopic levels in an indoor lighting environment. None of the tested physiological measurements produced relevant information about the potential discomfort glare perceived in such environment.

Discomfort Glare Perception by Drivers—Establishing a Link between Subjective and Psychophysiological Assessment

“…Therefore, we recommend testing new car headlamps on driver samples using subjective as well as at least some objective physiological methods, in addition to the traditional goniophotometer tests performed in the automotive industry. In concordance with other research [16,20], our findings suggest that the relationship between subjective glare perception and the underlying physiological mechanisms is probably more complex than what can be assessed with single/individual psychophysiological methods. Inter-individual differences also seem to play a greater role in glare perception than was previously thought; based on our results, assuming that something such as a "universal" or "average" observer exists is probably erroneous.…”

“…A common tool used in this context is the de Boer 9-point rating scale [18], which has been subjected to many revisions over the years regarding the verbal descriptors of the perceived glare intensity, as well as the directionality of the scale (in the original version, "1" was described as "unbearable" and "9" as "unnoticeable", which was shown to be confusing for many research participants) [19]. However, the inclusion of physiological data in headlamp glare investigations in order to further validate subjective findings has not been as frequent as one would expect [20], given that these data have been widely used in research on driver fatigue [21] and glare in daylight/indoor conditions [8,22]. This might be due to the fact that many such studies have been done in the field rather than in a laboratory, but with the increased development of portable physiological signal acquisition devices, one could expect a change in the future.…”

Performance of a new device for the clinical determination of light discomfort

“…To date, different methodologies aiming to determine discomfort glare have been set [36,37]. In relative evaluation, two or more lighting conditions are compared using forced choice, rank, or adjusting method according to subject perception.…”

“…Either the light condition is labeled or the light condition is adjusted to reach a predefined label. Subjective scale is widely used [36,37], but other objective measurements such as pupil size can also be used [11].…”