Discomfort glare from electric light

Discomfort glare is an immediate occurrence and arises from light sources or luminaires whose luminance is greater than the eye can adapt to. It can also become noticeable after a period of time.

The degree of discomfort glare depends on several factors; the luminance and the size of the glare source, the position of the glare source in relation to the line of sight and the background luminance against which the glare source is viewed.

Consequently, when light planning the luminaire’s luminance should always be considered in relation to the background luminance. The closer the dazzling surface is to the eye, the greater the risk of discomfort glare.

In open luminaires, especially those for compact and other intense light sources with high luminous flux, it is generally the light source itself or a mirror image in the specular reflector that causes the glare effect. One way to reduce discomfort glare is to use satin matt reflectors and luminaires with a larger surface area.

Discomfort glare can also be reduced by increasing the luminosity on walls and ceiling of a room. This can be achieved in different ways:

  • Using luminaires with an uplight component.
  • Positioning the luminaire closer to the walls in the room.
  • The walls can be lit separately or the luminosity increased by choosing higher reflection factors on the wall surfaces.

Walls that appear brighter in relation to the visual object can create adaptation problems. The luminosity of the room surfaces should therefore be adapted to the visual conditions and be limited as described in the Luminance distribution and luminance limitations chapter.