Unit of luminous flux : Lumen (lm)


Luminous flux is a photometric measure of radiant flux, i.e. the volume of light emitted from a light source. Luminous flux is measured either for the interior as a whole or for a part of the interior (partial luminous flux for a solid angle). All other photometric parameters are derivatives of luminous flux. Luminous flux is measured in lumens (lm).


Luminous flux for a selection of artificial light sources:

Lamp Type

LBS

Luminous Flux (Φ) in [lm]

10W compact fluorescent lamp

TC-D 10W

600

20W energy-saving lamp

TC-EL 20W

1.200

18W fluorescent lamp

T26 18

1.350

100W incandescent lamp

A60 100W

1.380

26Wcompact fluorescent lamp

TC-L 24W

1.800

100W low-voltage halogen capsule lamp

QT12 100W

2.300

36W fluorescent lamp

T26 36W

3.350

100W high-pressure sodium lamp (color corrected)

HST 100W

4.700

58W fluorescent lamp

T26 58W

5.200

70W metal halide lamp (nw)

HIT 100W

5.500

125W high-pressure mercury lamp

HME 125W

5.700

250W metal halide lamp (nw)

HIT 250W

20.000

The precise values depend on the brand involved, although the figures are always very similar.

The ratio between luminous flux and the power consumed is known as Luminous Efficacy.


Not all the luminous flux emitted by the lamp reaches the work plane. There are losses in the luminaire (absorption, transmission, reflection losses) and at the room perimeters (reflectance). In the normal case about 60-70% of luminous flux will reach the work plane (light output ratio).