The first thing that should be noted when buying a light for duty is its primary function. Even if it’s meant to be multi-purpose, your flashlight must meet your various duties, not those of another officer with a different detail.
If you work primarily where there are large areas to search, such as a warehouse or a field or down the street, a bright light is a must. If you work in the tight quarters of a house, parking garage, etc., you may want to consider a light with a bit less output. As I was told by my friend Walt Rauch—a fellow gun scribe, retired cop, and former Secret Service man—when using bright lights indoors, remember they will reflect off mirrors, metallic bangles, and china cabinets, blinding you and those behind you. This effect makes you and those with you useless until your eyes recover from this blast of white light.
If you need a duty light for your belt, I suggest any of the one-inch diameter two- or three-cell CR123A lights. These will be small enough to carry on your duty belt, yet won’t weigh a ton or be so large as to get in the way. The six- or nine-volt offerings are available in LED or any number of xenon halogen or other white light configurations.
Most of these lights put out an ample amount of light but, in some cases, it’s too much. Lights of the six- or nine-volt size have a lumen output of 60 to more than 150 lumens (lumens equals total energy output of a light; candle power equals the total brightness of the light). In rough terms a 65-lumen six-volt lamp provides enough light for me to clearly read the average team logo on a sweatshirt in the far corner of my yard, which is 40 yards from my door. This is enough light to see items in a subject’s hands and be able to tell the difference between a Motorola Razor and a Kel-Tec 9mm pistol.
LED vs. Xenon