The Luminous Flux is energy.The energy is the total amount of light energy radiated from a light source in all directions. The luminous flux is measured in lumens and is the parameter used to describe the “brightness” of a projector.
Fig 3
One lumen is the Luminous Flux or expressed more simply, the total amount of light energy emitted into one solid angle or steradian (see definition below), by a point source having a luminous intensity of 1 can
