Introduced in 2009, ANSI FL1 standards for flashlights ensure that models are tested and rated in the same way. Compliance with these standards is voluntary and the manufacturers do their own testing, but most major brands now include the following performance data on their packaging.
Measured in lumens. This is a measure of the intensity of the light coming out of the flashlight, on the highest brightness setting powered by new batteries. It may also be shown for multiple light settings. This is a great comparison tool, but does not tell the whole story about brightness. Beam intensity, distance and type all influence the effectiveness of a light in different applications. Light output can range from a modest 20 lumens (great for reading a book) to a terrain-scorching 3500 lumens.
Measured in meters. This is how far the light will shine before the brightness diminishes to the equivalent of the light from a full moon. Full moon illumination is considered adequate for safe and careful travel outdoors. This distance will vary with the brightness setting selected.
Measured in hours. How long does it take the light output to drop to 10% of the rated output on new batteries, rounded to the nearest quarter hour. Light output may gradually decrease over time, or remain largely constant and then suddenly decrease. Run time is commonly given for each light setting. A Runtime graph, if available, provides the best illustration of the performance of a light over time.
Measured in meters. Lights are tested by dropping them 6 times onto concrete at the rated distance. This test is primarily to ensure the light remains functional after occasional accidental drops. It is not a test of resistance for a light being run over, being struck with a heavy object or being used to strike other objects.
Rated using the IPX system. Water resistance is important if using your light in the rain or around bodies of water. Three ratings are used:
Indicates an IPX4 rating, which is splash resistant from all angles, after the impact test has been applied.
Indicates a water submersion rating, also after the impact test.
IPX7 – temporary immersion: up to 30 minutes at a depth of 1m.
IPX8 – submersion: up to 4 hours at the specified depth.