Runtime
How long a lamp runs on a given setting before the battery fades. Always check the number for medium, not maximum.
Manufacturers quote runtime per mode, and the spread between them is enormous. The same lamp might run three hours on high and forty on low. Maximum brightness drains any battery quickly and most lamps automatically step down from it within a few minutes anyway.
The number worth comparing is medium output, since that is where a headlamp actually spends its life. A lamp that gives eight hours on a usable medium setting will get you through a night session; one that gives two will not.
Regulated output is the other thing to look for. A regulated lamp holds brightness steady and then drops off sharply near the end; an unregulated one dims gradually the whole way, so half its runtime is spent being too dim.
Carry a spare battery or a small power bank for anything longer than an evening session. Runtime figures are measured at room temperature and cold cuts them.
Related terms
Where this comes up
The guides that use runtime and show it on real gear.
Runtime is one of 206 terms in the glossary.
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