Luminous flux

Luminous flux, or simply brightness, is denoted by the unit lumen (lm). Thus, an ordinary 100W incandescent bulb has about 1000 lumens, a T8 58W fluorescent lamp 5200 lumens. The unit lumen has become more important with the spread of LED and energy-saving lamps, since it is not possible to infer lumens from watts as with incandescent lamps. In general, the higher the lumen value, the brighter the lamp.