Beam angle

What exactly is a beam angle?

The Beam angle describes the angular range within which light emanates from a light source. It determines the extent of the resulting light cone and specifies how widely or narrowly the light is distributed in space.

The beam angle is measured in degrees (°) and is a key parameter for describing light distribution.

Relationship to the half-value angle

In practice, the beam angle usually corresponds to what is known as the half-value angle. This angle defines the range within which the luminous intensity reaches at least 50 percent of its maximum value.

Outside this region, the light intensity continues to decrease. The outer edge of the light cone, where the light intensity is lower, is referred to as the field angle. The half-angle and the field angle thus together describe the visible extent of the light.

Effect of Angle on Light Distribution

A small beam angle produces a narrow, highly concentrated beam of light. The light is directed specifically in a certain direction and illuminates a clearly defined area.

A wider beam angle results in a broader light distribution. The light cone covers a larger area and provides more even illumination.

Very wide beam angles allow for nearly uniform light distribution in many directions, eliminating the formation of a clearly defined beam of light.

Distinction from the cut-off angle

The beam angle must not be confused with the Cut-off angle be confused. While the beam angle describes the geometric distribution of light, the cut-off angle refers to the limitation of glare and visual comfort.

The cut-off angle indicates the maximum angle at which a light source is shielded to prevent direct glare. Both terms refer to different photometric properties and serve different functions in lighting design.

Implications for Lighting Design

The beam angle affects the size of the illuminated area, the intensity distribution within the light cone, and the spatial lighting effect. It is a fundamental parameter in the design and evaluation of professional lighting systems.