Defining the luminous flux
| symbol | F | unit | lm |
The luminous flux measures the total light output of a lamp or luminaire. Its unit lumen can also be expressed as cd sr. This indicates that the flux is essentially the sum (or, better, the integral) of the luminous intensity over all solid angles.
Defining the luminous flux
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Luminous
flux of some typical light sources
(GLS and SOX courtesy of Philips Lighting)