Beam Angle: Which Angle is Suitable?

Angle of incidence equals angle of reflection - this simple basic rule is probably still familiar to many people from their school days. By means of reflections in the light bulb, the beam angle of bulbs can be influenced almost as desired. In the case of so-called reflector bulbs, this results in a specific beam angle for the light emission.

The smaller this angle, the greater the concentration and thus the candela value for luminous intensity, which is defined as luminous flux per solid angle. As a lamp buyer, however, it is not enough to know the beam angle - the distance of the lamp from the illuminated object is also of fundamental importance, because the size of the illuminated area increases with increasing distance.

Most halogen reflector lamps have a beam angle of 35 degrees. LEDs, which emit directional light anyway, often use a lens that allows the beam angle to be set to a value between 25 and 120 degrees.

The brightness Distribution in the Beam Angle

Another term for the beam angle is the half-value angle. This is because within the beam angle there must be at least half of the (punctual) maximum luminous intensity emitted! If you know the values for lumens and beam angle of your new lamp, you cannot necessarily deduce from this exactly how the brightness is distributed. Even outside the room area in the beam angle, there may still be a high level of brightness. If you want to know exactly, you should look at the light distribution diagram of the lamp. This represents a two-dimensional cross-section through the three-dimensional light distribution curve.

The beam angle is of great practical relevance for reflector lamps, for example. For an initial comparison of the brightness and distribution of two lamps, the values of lumens and beam angle are usually sufficient - especially as the shape of the lamp often provides a decisive indication.

Which Beam Angle for Which Purpose?

In most living spaces, a wide angle of up to 120 degrees is recommended for basic lighting. For targeted illumination of specific path areas, 90 degrees have proven successful. Accent lighting and directed light, for example from a reading lamp, usually have a much smaller beam angle.

Two examples (distance between lamp and object is 2 metres):

• 15 degree beam angle: 60 x 60 cm area
• 60 degree beam angle: > 2 x 2 m area