This refers to the angle that arises between the ceiling of the room and the radiation area of the luminaire. The light cone is relatively wide with a low beam of 30°, while a low beam angle of 50° is correspondingly narrower and more focused. Or to put it another way: If the cut-off angle increases, the visual comfort of the lamp increases due to increased glare limitation. For recessed ceiling lights (downlights), the light cones on the wall are different if the lights are arranged in the same way. With a cut-off angle of 40°, the best possible compromise is achieved between the necessary horizontal illuminance on the floor and vertical illuminance on the wall.
This is why computer workstation lights need a beam angle of 40°. Vertical illuminance is important, for example, in sales rooms where products need to be well lit. With downlights with a beam angle of 30°, the maximum of the luminous flux is emitted at a high lateral angle. Downlights with a beam angle of 50° achieve a very high level of visual comfort for high rooms with their narrow light distribution. Wide-beam recessed ceiling lights can overlap their light cones, thereby increasing the overlapping illuminance. Since the light pattern results from the addition of all the lights, the lighting effect of a single recessed ceiling spot is difficult to assess when sampling.
