Definitions of units for luminous flux


Unit of luminous flux (symbol lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian


SI derived unit of luminous flux by its definition (symbol cd·sr).

mean spherical candlepower

When a light source distributing its luminous flux uniformly in all directions, and this uniform distribution having a luminous intensity of one candle in every direction, then the light souce has one unit of mean spherical candlepower (symbol MSCP). Lumens = 12.57 (4 π) x Mean spherical candlepower.