Overhead Glare and Visual Discomfort

Boyce, P.R.; Hunter, Claudia M.; Inclán, Carlos M. Cruz

doi:10.1080/00994480.2003.10748406

Cited by 25 publications

(28 citation statements)

References 1 publication

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“…It was a seven-category scale: 1 (Imperceptible), 2 (Just perceptible), 3 (Noticeable), 4 (Just uncomfortable), 5 (Uncomfortable), 6 (Just intolerable) and 7 (Intolerable). 11,12 Observers then proceeded to another condition.…”

Section: Methodsmentioning

confidence: 99%

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Assessing glare. Part 2: Modifying Unified Glare Rating for uniform and non-uniform LED luminaires

Yang

Luo

2016

Lighting Research & Technology

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This paper proposes a new glare model for assessing discomfort glare caused by LED luminaires having different luminance uniformities. It has been derived from the glare rating data for different groups of LED luminaires representing different degrees of luminance uniformity. In total, 5040 glare ratings were collected. Unified Glare Rating was tested using these data. It was found that Unified Glare Rating under-estimates the glare perception produced by non-uniform luminance glare sources. Furthermore, two modified Unified Glare Rating models proposed by Tashiro et al. and by the present authors were tested. They both performed well when predicting the results for LED luminaires having different luminance uniformities.

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Section: Methodsmentioning

confidence: 99%

“…Then, three different Contrast definitions generally applied in image processing area are modelled, as shown in equations (10) to (12).…”

Section: Relation Between Ugr and Observer Ratingmentioning

confidence: 99%

Assessing glare. Part 2: Modifying Unified Glare Rating for uniform and non-uniform LED luminaires

Yang

Luo

2016

Lighting Research & Technology

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“…The normalized luminance distribution over the exit window is shown in Fig.1b. During the experiment, subjects were asked to evaluate the discomfort glare of the various light conditions in 2 ways: on the seven-point rating scale (see Table 1), which is the same rating scale as used by Boyce and Ngai in their research [2,3]; and by indicating whether the lighting condition was comfortable or not.…”

Section: Experimental Designmentioning

confidence: 99%

P.30: Effect of the Correlated Color Temperature of Light on Overhead Glare in Offices

Zhang

Yan

Liu

et al. 2013

Symp Digest of Tech Papers

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We performed a subjective experiment measuring perceived overhead glare from a fluorescent luminaire with either a Correlated Color Temperature (CCT) of 4000K or 6300K. The group of 18 participants was equally divided over males and females, and almost equally over subjects wearing glasses and subjects without glasses. The results show that a light source with a higher CCT induces statistically significantly more overhead glare. In addition, differences in perceived overhead glare cannot be attributed to either gender or visual correction means.

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“…2 Glare formulae such as Visual Comfort Probability (VCP) and Unified Glare Rating (UGR) have assumed that light sources outside the direct field of view do not contribute to the glare response. However, more recent glare research has shown that individuals also sense discomfort from luminaires above the field of view, up to 85° above horizontal when the light source luminance is very high relative to the adaptation luminance (Ngai and Boyce 2000; Boyce et al 2003). Those angles are measured from a fixed horizontal line of sight.…”

Section: Glarementioning

confidence: 99%

“…The Guth Position Index assumes that when the luminaire is above the natural cutoff of the human facial features (approximately 53° above the line of sight, depending on the face), and is therefore not in the visual field, that it is no longer contributing to the glare sensation. Work on overhead glare (see Ngai and Boyce 2000; Boyce et al 2003) has shown that subjects report discomfort from sources located at angles up to 85° above the line of sight in interior applications. The same is likely true for outdoor applications as well.…”

Section: Metrics Related To Glare Perceptionmentioning

confidence: 99%

Pedestrian Friendly Outdoor Lighting

Miller

McGowan

2013

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Executive SummaryNighttime outdoor lighting has most often been designed for the vehicle driver, rather than the pedestrian. Metrics such as pavement illuminance or luminance, illuminance uniformity ratios, vertical illuminance on objects or faces, and glare metrics such as Veiling Luminance Ratio or Glare Ratings from the Illuminating Engineering Society (IES) Luminaire Classification System (BUG) have been used as criteria. The U.S. Department of Energy GATEWAY Demonstration Program has followed two pedestrian-focused projects at sites where the pedestrian-scale lighting needed improvement: Stanford University in California and the Chautauqua Institution in upstate New York. The results from these projects reveal that pedestrians may have different criteria and priorities than drivers, especially in areas where cars are subordinate to bicycles and users on foot.At both sites, an iterative process was used to evaluate luminaires; collect feedback from residents, homeowners, and/or campus facilities groups; and use that feedback to try other options. In both cases, it became clear that users• cared about the daytime appearance of the luminaire• found luminaire glare to be a significant factor in luminaire acceptability• preferred luminaires that produced a soft-edged pattern of light on the ground• preferred a warm color of light (2700K to 3000K) given the character of their neighborhood and the fact that they were used to either incandescent sources or high-pressure sodium as a baseline• found that horizontal illuminances could be at the low end of IES-recommended levels as long as luminaire glare was reduced.Diffusion was an important characteristic of optical systems deemed less glaring. Light-emitting diodes (LEDs) or clear metal halide arc tubes exhibit high variation of luminance across the face of the luminaire, but diffusion from frosted refractors and flat glass panels was judged as less glaring, even when measured spot luminances were high. Smoothing out the luminance transition from high to low resulted in responses of greater visual comfort, even though glare metrics do not take this into account.Traditionally, the outdoor luminaire's "glare" angles have been 75° to 90° from nadir. These projects gathered observations and responses that suggest that although pedestrians may be affected by glare from these angles when they are far away from a post-top luminaire, they are most uncomfortable when they are walking within the zone from 0° to 75°, that is, when they are closer to the luminaire and when the highest luminance elements are within or even above the field of view. This may be related to overhead glare that has been studied in interior applications, or it may be related to the fact that pedestrians naturally glance around their surroundings as they walk, putting the luminaire in the field of view as their eyes look upward.Every outdoor lighting project is different. The needs vary according to the project client, the users, and their activities, and therefore the best lighting solution will also...

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Overhead Glare and Visual Discomfort

Cited by 25 publications

References 1 publication

Assessing glare. Part 2: Modifying Unified Glare Rating for uniform and non-uniform LED luminaires

Assessing glare. Part 2: Modifying Unified Glare Rating for uniform and non-uniform LED luminaires

P.30: Effect of the Correlated Color Temperature of Light on Overhead Glare in Offices

Pedestrian Friendly Outdoor Lighting

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