Wonwoo Kim

Effect of Background Luminance on Discomfort Glare in Relation to the Glare Source Size

Discomfort glare from bright luminaires or windows is not a simple matter but consists of a complex relationship between a number of factors. The objective of this study was to investigate the effect of the background luminance on discomfort glare in relation to the size of the glare source. An experiment was conducted with observers. In the experiment, the change in the discomfort glare, depending on the change in the background luminance, was measured using different sizes of glare sources. Seven sizes of steradian of the glare source were selected and five levels of background luminance were chosen for the experiment. The results showed that the higher the background luminance, the smaller the observer’s degree of discomfort glare. The exponent of background luminance changed clearly into different patterns in relation to the sizes of the glare source. A new mathematical formula has been developed by this study to determine the exponent of the background luminance for use in the range from 0.0003 to 5 sr of the glare source. The use of this formula would extend the application limit of the current unified glare rating formula from the current limit of 0.1 to 5 sr. Using the formula, the change in the background luminance would have no impact on the discomfort glare, in case when the glare source occupies the entire visual field.

The Scope of the Glare Light Source of the Window with Non-uniform Luminance Distribution

This paper presents a methodology to determine the area of the glare light source on the window with nonuniform luminance distribution. Experiments with observers were conducted in order to evaluate discomfort glare using a simulated window with a nonuniform luminance distribution. The simulated window is divided into three parts, each of which has a different luminance so that the window surface would have a non-uniform luminance distribution. Discomfort glare was evaluated in 21 different combinations of the luminance conditions. Hopkinson’s multiple-criterion was used for the evaluation; and 27 observers had volunteered for the test. The results of this study can be used to determine how much the luminance should be in the area around the window in order to reduce discomfort glare from the window. If the luminance around the window was less than 40% of the maximum luminance of the sky seen through the window, this would reduce discomfort glare. If the luminance around the window was higher than 40% of the maximum luminance of the sky seen through the window, the area around the window could be considered as a glare light source.

The Variation of the Glare Source Luminance According to the Average Luminance of Visual Field

This study was conducted to propose a method of identifying glare sources from windows. Discomfort glare from windows of a classroom was evaluated in the experiments involving subjects, and the features that made the subjects recognize the glare sources in the windows were explored. The results of the evaluation led to the realization that the subjects regarded the patches that were causing discomfort glare as the glare sources on windows. It means that the patches having low luminance were not the causes of discomfort glare and were excluded from glare sources for the discomfort glare evaluation. There was a linear relationship between the average luminance of the visual field and the average luminance of the glare patches. The linear relationship has been expressed by a formula. The proposed formula has made it easier to identify the glare patches from windows. The approach as suggested in this study is distinctive to the others by the fact that the glare source was determined based on the average luminance of the visual field.

A Position Index Formula for Evaluation of Glare Source in the Visual Field

The purpose of this study was to propose a formula of the position index for evaluation of the glare source in the whole visual field. The glare sensation was measured to create the formula in binocular and monocular vision. The results showed that there is not a big difference in the level of discomfort glare sensation between the left and right eyes while the lower visual field is more sensitive to the discomfort glare than the upper visual field. Based on the borderline between comfort and discomfort luminance distribution in the whole visual field obtained through a series of experiments, position index was created, which was then turned into a formula. When predicting or evaluating the discomfort glare generated from the indoor or outdoor lighting with a computer, this formula would be of great help in easily identifying a position index. The findings of this research would provide important basic data for the evaluation of discomfort glare.