Definition
Beam angle is the angular spread of light from a directional luminaire, defined as the angle between the two directions where the luminous intensity drops to 50% of the maximum (center beam) value. A narrow 15° beam concentrates light into a tight spot (high candela, small coverage area), while a wide 120° beam spreads light broadly (low candela, large coverage area). Beam angle, combined with mounting height and aiming angle, determines both the size of the illuminated area and the illuminance (lux) at the target. In lighting design, beam angle is the primary selection criterion for accent, display, and directional lighting — it controls what gets lit and what stays in shadow.
Key Data
| Parameter | Value / Explanation |
|---|---|
| Very narrow: 8-15° | Spot/accent — jewelry, artwork, architectural details. High drama, small coverage. |
| Narrow: 15-30° | Accent/task — retail displays, feature walls. Focused attention. |
| Medium: 30-60° | General accent — merchandise areas, workstation task lighting. Balanced. |
| Wide: 60-90° | Flood/general — area illumination, wall washing. Broad coverage. |
| Very wide: 90-120° | Wide flood/ambient — warehouses, open areas, UFO high bay. Maximum coverage. |
Application Guide
Jewelry counter
12-15° narrow spot, 3,000-5,000 cd, CRI 95+
Tight beam creates sparkle and brilliance; isolates individual pieces from background
Retail clothing rack
25-35° medium flood, 1,000-2,000 cd, 3000K, CRI 90+
Wider beam illuminates the full garment; warm CCT flatters fabrics
Warehouse aisle (30ft)
90-120° wide flood, 28,000 lm UFO high bay
Maximum coverage from a single mounting point; uniform illumination across the aisle width
Conclusion & Procurement Recommendation
Beam angle selection in B2B procurement must account for mounting height: beam diameter = 2 × height × tan(beam angle/2). At 3m mounting height, a 25° beam creates a 1.33m diameter spot; at 10m height, it creates a 4.4m spot. Key specifications: (1) Request the complete candela distribution table (IES file) — '25° beam angle' can vary by ±3° between manufacturers due to different measurement conventions, (2) Specify beam angle AND field angle (10% intensity cutoff) — the field angle determines the visible edge of the light pool, (3) For museum and gallery applications, specify beam edge sharpness: 'hard-edge' vs 'soft-edge' vs 'framing projector' for precise rectangular beam shaping.