With the increasing penetration of LED lighting, not only in the home but also in specialized equipment, the lumen (lm) is massively introduced as a light-producing unit. Many people are accustomed to associating the power of light with watts (W) because of the standard incandescent bulbs that are widely used. But the wattage that is put on their packaging indicates the amount of energy they consume, not the brightness of the light. The LEDs used by LEDs produce much more light, with significantly less energy than a conventional light bulb. And the lumen is the internationally accepted unit for measuring the brightness of a light source.
The exact definition of a lumen is that a lumen is equal to the luminous flux emitted by a point source at a spatial angle of 1 stradian at a light intensity of 1 candelas. To put it simply, a lumen equals 30 square inches of lit candle space. Accordingly, the more lumens are, the brighter the light.
To give you a clearer idea, one practical example - a standard 40W incandescent bulb emits a light flux of 450 lm. By comparison, an LED bulb that emits 450 lm is usually between 6 and 9 W. This ratio of watts to lumens is called light output. You can use it as a way to compare different luminaires.
As an example, in terms of equipment - flashlights with a brightness of about 50 lm are for general use, such as lighting the road directly in front of you when moving at night; tactical lanterns used by police and military units typically start at 100 lm; shuttles used for night cycling should be 200-300 lm; projector type flashlights start from 1000 lm.
When making your choice of lighting equipment, you should first and foremost be aware of the exact purposes for which it will be used. In addition to the brightness, you should also consider the economy, weight, shape of the appliance, batteries, beam length, water resistance, and more.