Lumens and Candela can help you understand the two fundamental characteristics of a tactical light's beam pattern: throw and spill. Throw is the light's ability to reach out to far distances, like when you're trying to see what's across a field or in a tree line. Most of your throw will come from the intensity of a light's center 'hotspot'. Spill is the peripheral light outside the hotspot. Spill light won't have much range, but it can be lifesaving in close-quarters, where threats often in the corners of a room. To understand how Lumens and Candela can inform your understanding of how a light will perform, let's give an example. If two weapons lights have a 500-Lumen output, but one light has a higher candela, its concentrated beam will be more intense and make up a larger percentage of the light's overall lumen output. A 500-Lumen light with a higher Candela rating will send more of its power out into the distance, allowing you to see further. The 500-Lumen light with a lower Candela measurement will cast more of its lumen output into the spill light, making the center hotspot less powerful but offering more ambient light at your periphery.