Lumens are a unit of measurement that describes a light’s total light output.
For tactical lights, having more output is always a good thing. If you’re trying to fill a dark room and identify potential threats, you’ll need a high-output light that can illuminate the room from corner to corner. Lumens are a good basic measurement to compare different lights by overall output—but Lumens don’t tell the full story. For example, lanterns may produce a lot of light overall, but in a tactical setting, only a small portion of that light will be useful.
To fully understand a light’s practical output, you’ll need to understand its beam pattern and Candela rating.