What is glare in LED stadium lighting?
Glare is a phenomenon where an unsuitable distribution or range of brightness within the field of view causes visual discomfort, eye fatigue, or reduced visibility. In stadium lighting, glare primarily stems from light shining directly into the eyes from the fixtures themselves (direct glare) and light reflected off smooth surfaces such as water or flooring (reflected glare).
Glare negatively affects both athletes and spectators: athletes may struggle to see the ball or their opponents, increasing the risk of injury, while spectators may experience eye discomfort, detracting from the viewing experience. Methods to control glare include:
First, employing cut-off light distribution. Through lens or reflector design, the light output is strictly confined to a specific projection angle; beyond this angle (e.g., an angle greater than 65° from the vertical), the light intensity drops rapidly to near zero. This design is known as "full cut-off" or "semi-cut-off."
Second, increasing the mounting height. The higher the fixtures are mounted, the greater the angle of incidence, thereby reducing the likelihood of light shining directly into the eyes.
Third, using glare shields or louvers. Adding physical shielding panels in front of the fixtures helps block stray or scattered light.
Fourth, selecting appropriate fixture locations. Avoid installing fixtures directly within the athletes' line of sight when they look upward (such as the direction a soccer goalkeeper looks when taking a long goal kick). Generally, a downward tilt angle of at least 15° to 25° is required for all fixtures.
Fifth, controlling the surface brightness of the fixtures. Using matte finishes or black coatings helps reduce reflections from the fixture housing itself.
Sixth, using digital dimming to lower brightness in non-critical areas. Intelligent control systems can be used to appropriately reduce the output of fixtures likely to cause glare while the game is in progress. International lighting standards quantify glare using the "Glare Rating" (GR); for stadiums, the GR is typically required to be below 50 (with some sports requiring it to be below 40).
When purchasing LED stadium lights, one should examine their light distribution curves and glare control specifications.
