Specification guide

Beam angles: getting the specification right

Beam angle is one of the most consequential decisions in a lighting specification, and one of the most commonly under-considered. The fitting, the lumen package, and the colour temperature can all be right. The wrong beam angle will still compromise the result.

What does beam angle actually determine in a scheme?

Beam angle controls light distribution across a surface. It determines coverage area, intensity at a given point, and how fittings need to be spaced to achieve target lux levels.

The relationship between beam angle, mounting height, and lux output is what drives photometric calculations. A narrower beam concentrates the same lumen package into a smaller area, increasing intensity. Widen the beam and that intensity spreads across a larger footprint, reducing it. Neither is inherently better. Both need to be matched to the application.

How does mounting height affect beam angle selection?

Mounting height is the primary variable. It determines the illuminated diameter at floor or task level, which directly informs spacing and the number of fittings required.

At standard commercial ceiling heights of 2.4m to 3m, a 60 to 90 degree beam delivers practical coverage for ambient schemes. Above 4m, the same angle spreads too wide before it reaches the work plane, reducing effective lux levels significantly. Tighter angles in the 30 to 45 degree range are more appropriate at height, with spacing calculated accordingly.

It is also worth noting the interaction between beam angle and maintained lux targets. A fitting specified on peak lumen output at a wide angle may fall short of the required lux level at the work surface once the beam has dispersed. Photometric data, not just the spec sheet, should inform the decision.

What beam angles are typically specified for commercial office schemes?

General ambient in open plan sits at 60 to 90 degrees. Task zones typically require 30 to 45 degrees for adequate intensity at the work surface.

When does beam angle selection require lighting design input?

Any scheme with variable ceiling heights, mixed task requirements, or lux level compliance obligations benefits from a full photometric calculation rather than rule-of-thumb selection.

Beam angle errors are among the most common causes of post-installation remedial work on commercial fit-outs. The specification looks correct on paper, but the photometric reality does not match the design intent. Running the numbers before committing to product selection avoids that outcome.