FIELD MEASUREMENTS OF ILLUMINANCE AND LUMINANCE DISTRIBUTION

Evaluation of visual environment in gymnasiums part 1

Abstract

 LED lighting technology has been seeing increasing use in sports facilities. LED lighting has characteristics such as a small light-emitting area and high directionality, which may cause glare. The JIS Recommendation for sports lighting provides recommended values for illuminance and uniformity as well as glare for outdoor sports facilities. However, it does not determine the recommended value for glare in gymnasiums. The purpose of this study is to reduce glare from luminaires in visual field during sports competition in gymnasiums. In this paper, measurements of light environment were carried out in eleven gymnasiums (six with LED lighting and five with HID lighting).

 In order to evaluate glare felt during sports, the luminance distribution of players’ visual fields and that of the light-emitting area of the luminaires as well as illuminance distribution were measured. Measurements were conducted assuming a badminton game in which players may look at luminaires directly. The illuminance distribution was measured based on JIS method. The luminance distribution was measured by digital cameras. To measure the luminance distribution of players’ visual fields, a wide-angle lens was used, while a narrow-angle lens was used for the measurement of the luminance distribution within a luminaire. Since the line of sight of a player always moves, the luminance distribution of visual field was measured to cover various elevation angles at a measurement point on the court. Since the luminance distribution of a luminaire differs depending on the relative position between the luminaire and an observer, the luminance distribution of the luminaire was measured from different observers’ positions.

 In the results of measured illuminance distribution, four of the eleven gymnasiums had higher than 750lx of average illuminance (JIS classification is I), three of the eleven gymnasiums had higher than 500lx and lower than 750lx (JIS classification is II), and the final four of the eleven gymnasiums had lower than 500lx (JIS classification III).

 Since the maximum luminance value of the visual field cannot be measured precisely, measured luminance distribution was evaluated by percentile value in this study. In the result of measured luminance of the visual field with a 90-degree elevation angle, the 0.1% tile values of the luminance were higher than 40,000 cd/m² in 68% of the gymnasiums. Analysis of 0.1% tile, 0.5% tile and 1% tile values of luminance in the visual field showed that the luminance in the visual field was increased as the elevation angle increased. Analysis of 0.1% tile, 0.5% tile, 1% and 50% tile values of luminance in the visual field showed that the luminance in the visual field was increased as the facility grade classification increased.

 Since it is difficult to determine the light-emitting area in luminaires, the area with higher than 1,000 cd/m² of luminance is considered a light-emitting area. In larger than 60-degree elevation angles, the average luminance of light-emitting area (area with higher than 1,000 cd/m² of luminance) was higher than 20,000 cd/m² in all gymnasiums. A significant difference in average luminance of the light-emitting area between the elevation angles was found. At all the elevation angles and all facility grade classifications by JIS, the average luminance of the light-emitting area in the gymnasium with LED lighting was significantly higher than that of the light-emitting area in the gymnasium with HID lighting.