Here's a quick and dirty explanation of some of the terms.


Lumens == Total light output. Imagine dumping out a salt shaker onto a table. Lumens would be a measurement of the total amount of salt.

Candela aka candlepower == Maximum light output at the brightest part of the beam. In the salt metaphor, this the height of the tallest pile of salt.

Throw == How far a flashlight can be used to spot an object. Candela is a good way to compare throw between flashlights.

Flood == How well a flashlight illuminates a large area close to you, generally viewed as opposite to throw.

Emitter == The part of the flashlight that glows when you put current through it.

LED == Light emitting diode. An electric lighting technology that is far more energy efficient and generates less heat than any others, with emitters that last a long time (50,000 hours is a common rating) and are extremely shock-resistant.

Incandescent, or incan == A classic lightbulb. Less efficient and far less shock-resistant than LEDs, incans typically provide better color rendering.

LED flux bin == A measurement of how many lumens are output at a given current for a run of LED emitters. R bins are more efficient than Q bins, and Q5 bins are more efficient than Q4 bins. The most efficient I've seen so far is U2. This is an area of rapidly improving technology, so the amazing Q5 binned flashlight I bought in March of 2008 is now far behind the times and relegated to my BOB.

CREE == A company that makes awesome LED emitters. Typically near or at the pinnacle of LED technology.

XR-E == An older line of CREE LED emitters.

XP-G == A somewhat newer line of CREE LED emitters, throwier than XM-L but not as much as XR-E.

XM-L == Floodier than XP-G but far more efficient, the current line of CREE emitters. Note that a flashlight's floodiness or throwiness is dependent in large part on the reflector technology and geometry.