paper Despite nearly a century of research, we are still unable to accurately predict discomfort due to glare.

The vast majority of discomfort glare research uses subjective evaluations – primarily category rating or luminance adjustment. This article discusses methodological issues which contribute to uncertainty in evaluations.

Fotios S. Research Note: Uncertainty in subjective evaluation of discomfort glare. Lighting Research and Technology, 2015; 47(3); 379-383.

paper It is unlikely that the commonly used procedures will ever reach resolution. This article raised suggestions for alternative procedures.

Fotios S. Correspondence: New methods for the evaluation of discomfort glare. Lighting Research and Technology 2018; 50(3): 489-491.

paper Evaluations of discomfort using category rating were compared against involuntary physiological responses.

Subjective evaluation of discomfort was highly correlated with eye movement and pupil constriction: Severe glare discomfort increased the speed of eye movement and caused larger pupil constriction.

Lin Y, Fotios S, Wei M, Liu Y, Guo W, Sun Y. Eye movement and pupil size constriction under discomfort glare. Investigative Ophthalmology and Visual Science, 2015; 56(3); 1649-1656.

paper A series of experiments were conducted to explore the influence of variations in experimental design, the aim being to explain the variance between different studies.

In this first experiment we explored the influence of anchor bias in luminance adjustments.

Kent M, Fotios S, Altomonte S. Discomfort glare evaluation: The influence of anchor bias in luminance adjustments. Lighting Research and Technology 2019; 51(1): 131-146.

paper When Hopkinson used his multiple criterion scale, test participants used adjustment to set the luminance representing a defined degree of discomfort. One limitation was that the four degrees of discomfort were evaluated only in ascending order.

In this experiment we repeated Hopkinson’s method but also using descending and randomised orders of discomfort. The different orders led to significant differences in luminance for a given degree of discomfort.

Kent MG, Fotios S, Altomonte S. Order effects when using Hopkinson’s multiple criterion scale of discomfort due to glare. Building & Environment 2018; 136: 54-61.

paper When evaluating discomfort the test participant must look somewhere, and for evaluating discomfort from peripheral sources a fixation task is used. This experiment compared the use of a simple fixation mark and a task requiring a degree of cognitive attention. The results confirmed a lower degree of discomfort is expressed when engaged in a task demanding a higher degree of cognitive attention.

Kent M, Fotios S, Altomonte S. An experimental study on the effect of visual tasks on discomfort due to peripheral glare. Leukos. 2019; 51(1): 17-28.

paper Stimulus range bias is probably the greatest problem within subjective evaluations of magnitude. Here we demonstrate its influence on evaluations of discomfort from glare using adjustment. The conclusion, that range bias is significant, is not unexpected but direct demonstration helps to support the message.

Kent MG, Fotios S, Cheung T. Stimulus range bias leads to different settings when using luminance adjustment to evaluate discomfort due to glare. Building & Environment 2019; 153; 281-287.

paper When you ask test participants to evaluate a series of items which vary in magnitude, it has been proposed that first the range is demonstrated. In other words, before any evaluations, show participants the smallest and largest magnitudes they are about to evaluate. This helps anchor the response range to the magnitudes. This experiment was conducted to determine whether such demonstration would affect the evaluations.

Kent M, Fotios S. The effect of a pre-trial range demonstration on subjective evaluations using category rating of discomfort due to glare. Leukos. Online first, 23/07/2019.

paper Jan Wienold (EPFL) and several colleagues recently published a paper in which they tested several possible metrics for discomfort from daylight glare using a several independent sets of data. In terms of a robust analysis, this was outstanding work. In this item of correspondence I raised a few of questions. One question asked about fairness, given that the proposers of the two best-performing models are also authors of the analysis. A further question asked about stimulus range bias: the authors had suggested it was not a problem but that is unlikely to be the case.

Fotios S. Correspondence: Discussion of ‘The cross validation and robustness of daylight glare metrics’ Lighting Research and Technology 2020; 52(2): 314-317.

paper Glare can impair vision (disability) as well as causing discomfort.

This article describes an experiment conducted to investigate how disability glare can affect target detection.

Winter J, Fotios S, Völker S. The effects of glare and inhomogeneous visual fields on contrast detection in the context of driving. Lighting Research and Technology 2018; 50(4): 537-551.

On-Going work
Further articles have been submitted which investigate the influence on discomfort evaluations of showing a pre-trial demonstration of the stimulus range, and of the bias induced by stimulus range itself.