The term lumens is often mentioned in reference to flashlights, and most of us know by now that more lumens means more light output. But we've often wondered how this is this quantified, and how effective it is at determining real-world effectiveness of a flashlight. The article below from Breach Bang Clear explains some of the details behind this measurement, and also how it differs from other common lighting terms.
Editor's Note: The following article was originally published by our friends at Breach Bang Clear. It appears here in its entirety with their permission. For more from the Mad Duo and crew, go to BreachBangClear.com or follow them on Facebook or Instagram.
Term: Lumens
Relates to: Light intensity
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, 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 (i.e. perceived light power) 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 to measuring lumens, but the current industry standard is to use a integration sphere which completely diffuses any light source.
To really dive deep into the subject of lumens and flashlights you’ll want to read this post and this one.
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 total light output of a given source. In and of itself it offers no other performance information.