Beam Distance Chart

Beam distance decreases as a light's battery runs down. The ANSI FL1 Standard defines a light's battery life as the time it takes for the light output to drop to 10% of its initial value. Beam distance is proportional to the square of the measured intensity, so keep in mind that the battery life is not the time at which the beam distance decreases to 10% of its initial value.

The FL1 Standard defines beam distance as the distance at which the light would project 0.25 lux, which is equivalent to the brightness of the full moon on a clear night. This is determined by measuring a light's output in lux at a fixed distance in a dark chamber, and using the inverse square law to calculate the distance at which it would measure 0.25 lux.

For our battery life testing, lights are placed in a 2m long dark box with light-absorbing material on the walls. A calibrated light meter is then used to measure the output while the light runs. Fans are used to cool the light while it runs, because output often drops at high temperatures, and lights can put out a lot of heat.

This test only measures light output at a single point. The shape of the beam and efficiency of the optics will affect the total light output. Just because one light has a higher beam distance does not necessarily mean it puts out more total light.