What is the illuminance uniformity of high-mast lights?
Illuminance uniformity (U2—defined as the ratio of minimum illuminance to average illuminance) is a key indicator of lighting quality for high-mast lights. Since these systems typically feature multiple luminaires arranged in a ring—each with its own beam angle and aiming direction—high uniformity can be achieved through optimized design.
According to the Chinese industry standard CJJ 45-2015 (*Standard for Design of Urban Road Lighting*), the U2 uniformity for highway interchanges and public plazas should be no less than 0.4; however, specialized facilities such as ports and airports require higher standards, typically U2 ≥ 0.5–0.6. With high-quality LED high-mast systems, precise light distribution and aiming can push U2 values above 0.7. Key factors for achieving high uniformity include:
① Appropriate number of luminaires: Too few result in insufficient light-pattern overlap and dark zones at the edges, while too many lead to waste and potential glare.
② Suitable beam angles: High-mast systems often employ a mix of narrow-angle (10°–30°) and medium-angle (30°–60°) optics; inner-ring luminaires use wider angles to illuminate the near zone, while outer-ring luminaires use narrower angles for the far zone.
③ Luminaire tilt angles: The vertical (tilt) and horizontal (pan) angles of each luminaire must be precisely adjusted based on its specific location.
④ Asymmetric light distribution: Some high-mast lights utilize specialized asymmetric lenses to direct more light toward areas further from the mast, thereby compensating for light attenuation over distance. When purchasing high-mast lighting, it is advisable to request illuminance contour maps and false-color maps from the supplier to visually assess the uniformity.
