>> Light output Measured in lumens, this is the total amount of light the lamp emits (one lumen equals the light of one candle from one foot away). For basic camping and on-trail hiking, a device with 24 lumens is plenty. On trickier terrain—scrambles, off-trail routes, and canyons—invest in a lamp with 55 lumens. Cyclists and cavers might require 100-plus-lumen lamps—some floodlight models even deliver a whopping 350. But beware: Lumens reveal nothing about the beam’s quality, or how well it illuminates a distant object. If the lamp has poor optics, for example, it might diffuse the light in many directions, rather than in a useful, focused beam, so consider beam distance as well.
>> Beam distance This is the max distance the lamp usefully illuminates something (see above). Your lamp should shine 25 meters for basic trail hiking and 45-plus meters for climbing, orienteering, running, etc.
>> Modes Here’s a rundown of useful settings to look for:
> High/low power All but the most basic lamps let you choose between brightest (sucks the most juice) and economy mode (dimmer, but saves power). Some also offer a medium setting.
> Focused or wide-angle beam Typically, narrow beams travel farther than wide-angle ones, which disperse light into a broader area. Some headlamps convert between the two, either by using a diffuser lens to change the beam angle or by activating peripheral LEDs.
> Extra-strength pulses Some models let you amp light output by 50% for up to 20 seconds, gulping power but giving you a glimpse far ahead.
> Strobe Flashing lights signal rescuers.
> Color LEDs These preserve night vision—the eyes’ adjustment to low light. Full adaption takes 30 minutes, and bright light destroys it. Avoid lamps with a tinted screen you pull over white LEDs; this dulls the light.
>> Light source Unless you’re a caver, opt for LEDs over halogen bulbs. They’re not as bright, but they last much longer and won’t break.
>> Batteries Some lamps use coin-cell or camera batteries; these cut weight but not enough to justify hunting for these rarer types. For most uses, stick with regular alkaline or rechargeables. In cold weather, use lithium ion batteries, which work well down to –20°F or more. Alkaline batteries get sluggish in the cold, which slows the chemical reaction, and lose power 60% faster at 0°F than at 68°F.
>> Power usage Decide if you want a lamp with regulated or unregulated power. The former keeps the light output constant until the battery can’t support it; then output plummets to emergency light (some have low-battery indicators). Unregulated lamps slowly dim as the batteries lose juice, lowering beam distance but warning you of waning power.
Gear School: HeadlampsImprove your night sight with the latest headlamp technology.