The Effect of a Pre-Trial Range Demonstration on Subjective Evaluations Using Category Rating of Discomfort Due to Glare

Michael G Kent,Steve Fotios

doi:10.1080/15502724.2019.1631177

Michael G Kent, Steve Fotios

Open Access

https://doi.org/10.1080/15502724.2019.1631177

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Journal: LEUKOS	Publication Date: Jul 23, 2019
Citations: 8	License type: open-access

Affiliation: University of Nottingham, University of Sheffield

Abstract

ABSTRACT Category rating is a procedure commonly used to evaluate visual discomfort due to glare. One recommended step for good practise in a category rating procedure is to use a pre-trial demonstration (PTD) of the range of stimuli to be experienced. However, PTD have rarely, if at all, been used in past research on discomfort glare. In this study, two experiments were conducted to test the influence of the PTD on evaluations of discomfort due to glare. In the first experiment participants evaluated four glare source luminances with, and without, a PTD. The results suggest that using a PTD increased the reported degree of discomfort perceived for the same glare setting, although this may depend on the manner in which the PTD is presented. In the second experiment, participants evaluated four glare source luminances using PTD with three different luminance ranges: the results suggest this had significant effect on discomfort evaluations in that evaluations of discomfort were lower when a higher luminance range was used. Along with other recent studies, these findings suggest a need to derive a more robust procedure for measuring the discomfort due to glare.

Highlights

Category rating is a widely used procedure for evaluating the effect of changes in lighting on occupants’ evaluations of the visual environment
Within each of the four glare settings, there is a consistent effect of pre-trial demonstration (PTD) range in that the higher PTD range led to lower GRV (IES-GI), signalling less discomfort for the same luminance
It has been suggested that the range of stimuli should be demonstrated to test participants before asking them to provide evaluations using category rating (Adams et al 2004; Fotios and Houser 2009; Houser and Tiller 2003; Olkkonen et al 2014), here labelled a pre-trial demonstration (PTD)

Summary

Introduction

Category rating is a widely used procedure for evaluating the effect of changes in lighting on occupants’ evaluations of the visual environment. One suggestion for countering this is to demonstrate the range of stimuli before trials commence, to define to observers the meaning of the upper and lower limits of a rating scale, and anchoring the response range to the stimulus range (Adams et al 2004; Fotios and Houser 2009; Houser and Tiller 2003; Olkkonen et al 2014; Tiller and Rea 1992) This is referred to here as pre-trial demonstration (PTD). The mean luminance was held at a constant 65 cd/m2 throughout the experiment, as this is within the range of values commonly found in interior spaces (CIBSE 1994) Both the VDU and background lighting produced a correlated colour temperature (CCT) of 4000 K, which was recorded from the viewing position with a calibrated illuminance chromameter (CL-200a, Minolta, Japan, manufacturer’s reported accuracy ±2% lux and ±2% CCT)

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