Beam angle is the measurement, in degrees, of the spread of light emitted by an LED fixture. A narrow beam angle (15–30°) concentrates light into a tight spot. A wide beam angle (90–120°) spreads light broadly across a large surface. For trade show lighting, choosing the wrong beam angle is one of the most common reasons a booth ends up with hot spots, dark corners, or glare.
How Beam Angle Is Measured
Beam angle is measured as the angle between the two points where light intensity drops to 50% of its peak value. So a 60° beam angle means the light is at full intensity in the center and drops to half intensity at 30° on either side of center.
A related term is field angle, which measures where intensity drops to 10% of peak. Field angle is always wider than beam angle. Most product specs list beam angle, not field angle — so that's the number to focus on.
Beam Angle Guide for Trade Show Applications
| Beam Angle | Light Pattern | Best Trade Show Use |
|---|---|---|
| 15–30° | Tight spot | Spotlighting a single product, trophy, or hero item on a shelf |
| 45–60° | Medium spot | Illuminating a section of a display, accent lighting |
| 90–120° | Wide flood | Even coverage across a full graphic panel or backwall |
| 120–150° | Very wide flood | General ambient booth lighting, large open areas |
For most trade show display arm lights illuminating a backwall graphic, 90–120° is the standard choice. It produces even, shadow-free coverage across the full width of a graphic panel without hot spots.
What Happens If You Choose the Wrong Beam Angle?
Too narrow (e.g., 30° on a backwall graphic): You get a bright circle in the center of the graphic and dark areas at the edges and corners. The booth looks uneven and unprofessional. This is the most common mistake when exhibitors buy spotlights designed for retail product display and use them on a flat graphic panel.
Too wide (e.g., 150° on a small product display): Light spills beyond the target surface, illuminating the floor, ceiling, and neighboring booths. You lose efficiency — less of the light is actually hitting what you want to illuminate — and you may create glare for visitors in the aisle.
Beam Angle and Mounting Distance
Beam angle and mounting distance work together. The further the light is from the surface, the wider the illuminated area for any given beam angle. The formula is straightforward:
Illuminated diameter = 2 × distance × tan(beam angle / 2)
In practice, for a display arm light mounted 400mm from a graphic panel:
- 60° beam angle → illuminated circle of approximately 460mm diameter
- 90° beam angle → illuminated circle of approximately 800mm diameter
- 120° beam angle → illuminated circle of approximately 1,385mm diameter
For a 3m wide backwall with three lights spaced 1m apart, a 120° beam angle at 400mm mounting distance gives overlapping coverage with no dark gaps between lights.
Beam Angle for Specific Booth Types
Pop-up display with fabric backwall
Use 90–120°. The goal is even illumination across the full graphic. Fabric absorbs more light than rigid panels, so wider beam angles help compensate.
Product shelf display
Use 30–60°. You want focused light on specific products, not spill onto the shelf above or below.
Island booth with open sides
Use 90–120° for graphic panels, 60° for product spotlighting within the booth interior.
Lightbox or SEG frame
Lightboxes are internally lit — beam angle of the external arm light is less critical. If you're front-lighting a lightbox, use 90–120° for even coverage.
Frequently Asked Questions
Do all LED arm lights have the same beam angle?
No. Beam angle varies by model and is determined by the lens design. Always check the spec sheet. Most display arm lights designed for trade show backwall illumination use 90–120°. Spotlights designed for product display use narrower angles.
Can I change the beam angle after purchase?
Some fixtures accept interchangeable lenses that allow beam angle adjustment. Most standard arm lights have a fixed lens. If you need flexibility, look for fixtures with replaceable optics or buy separate units for different applications.
What beam angle do BOOTH LIGHTS arm lights use?
Our standard LED display arm lights use a 120° beam angle, optimized for even coverage across graphic panels and backwalls. This is the most versatile angle for general trade show use.
Read our full guide on how to choose a trade show display arm light, or browse our full range.