The lumen is the measuring of projectors’ brightness levels. When you are using a projector, it is important to look at the watts and lumens of the projector. The more lumens, the brighter the picture will be. Lumen is an abbreviation of luminous flux, which is a unit of radiometric measure of luminous intensity or radiant flux. If we talk about lux, it is used as a unit of measurement for light intensity. The lux unit is defined as the amount of light emitted from one square meter of surface.