Output Measurements

In a perfect world, every flashlight from every manufacturer would be tested and measured exactly the same way, using the same equipment, and results would be expressed in the same units of measure. But, unfortunately, the world is far from perfect. Candlepower refers to the single brightest spot of a beam, which doesn’t tell you much about beam quality or the amount of usable light as a whole. A lumen measurement is actually a quantity determined by measuring the total radiant power across the light’s spectrum and then correcting the data for the relative response of the human eye. It’s a more complicated measurement, but it’s also a more useful one for consumers because it gives an overall sense of the beam’s intensity. We aim to express outputs and runtimes as clearly as possible, generally stating them in terms of output with corresponding runtimes.

Single-Stage Lights

“High” lumen output is the maximum amount of light a flashlight will produce running on fresh batteries; it’s expressed in lumens. “Runtime” is how long a light will continue to produce useful levels of light; that means enough light to illuminate a map or find something inside a pack—around one lumen. So if a single-stage light’s “high” lumen output is listed as 80 lumens, and its “runtime” is 12 hours, that doesn’t mean it will produce 80 lumens of light for 12 hours. It will initially produce a bit more than 80 lumens, but output will eventually level off to a lesser but still substantial output level, then continue to decline to lower useful output levels before the battery power is completely depleted. Exactly how it drops is expressed in the light’s output/runtime curve. Quality LEDs are electronically regulated so their curves have less severe drop-off than unregulated lights.

Two-Stage/Variable-Output Lights

With two-stage or variable-output lights we list multiple output levels expressed in lumens: two for two-stage lights and normally three points of reference for variable. Then we list runtimes that correspond to each specific light output level. Since you’d probably not operate your light at one output level the whole time, your runtime will fall somewhere in the middle. That said, you won’t know exactly what your runtime will actually be, but at least you’ll have a reference for where your light’s runtime will fall. This will allow you to make decisions on how to run your light, based on how much power you want to expend, depending on your situation. It’s not a perfect science but it gives you the information you need to make vital decisions in the field, especially in the event of an emergency. Again, as with single-stage lights, your high output will eventually dip below the highest-rated lumen rating, but it will still provide substantial light for most applications.