Lumens Abbreviation: lm “A single unit of luminous flux in the International System of Units, that is equal to the amount of light given out through one steradian by a source of one (1) candela intensity radiating equally in all directions.”
Noun, plural lu·mens, lu·mi·na [loo-muh-nuh] /ˈlu mə nə/.
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Relates to: Light intensity (brightness)
Category: Tactics and equipment.
Application(s) of Use: flashlights, weapon lights, light bulbs—anything that emits light
Definition: a measure of the total quantity of visible light emitted by a source
Why it Matters: There are several different ways to measure light intensity, but lumens (symbol: “lm”) are the current gold standard.
Into the Weeds: We used to roll with candlepower, once upon a time expressed as candela, which is an old and obsolete measurement which assesses the amount of light falling onto a target rather than the total amount of light emitted. The lumen equivalent of candlepower is called lux, which is used to measure luminous flux per unit area.
Pre-fluorescent and LED bulbs often stated brightness levels in watts. Though this is an extremely dated method, many LED, and CFL bulbs will list watt equivalency numbers on the box—likely so your grandparents won’t be confused.
What’s particularly noteworthy about lumens is that it’s a measurement mostly used only for frequencies the human eye can detect, rather than the entire spectrum emitted by a given light source. There are several methods for measuring lumens, but the current industry standard is to use an integration sphere, which completely diffuses any light source.
[Yes, it looks like a time machine]
The TL;DR version is this: Higher lumens just means more light from the source, not necessarily a better flashlight or light bulb.
In Summary, a lumen is just a way to measure the total light output of a given source. In and of itself it offers no other performance information. There is much, much more to assessing the efficacy of a given flashlight — how it throws the light, how the lens and/or reflector affects the light it pushes, endurance/battery life, and of course the intended use of the light vis a vis flood vs. throw, i.e. the spill and reach of the light, etc.
Question(s) for the Crowd:
Are you a proponent of “the more, the better” on your fighting lights, or do you prefer different settings for different tasks?
Do you carry a WML off duty or daily carry?
Do you carry a handheld light every day, and if so, which one?
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Great little guide on Lumens! Hopefully now when I mention about lumens on my website I’ll guide people to this article. 🙂