See the Light

Nearly everyone who hunts has a small flashlight tucked in his pack or field kit--for emergencies, for getting in and out of stands or blinds in the dark, or for tracking game into the after-sundown hours. We've taken them for granted so long, in fact, that many of us have missed noticing there has been a revolution in flashlights in recent years, which has produced ultralight, ultracompact and ultrapowerful hand-held lights for hunters.

One of the most significant changes has been the lithium-battery-powered LED (light emitting diode). From tiny key-chain-size LED "emergency" lights to full-size flashlights, LED lights are popping up everywhere. They represent some great advances over traditional incandescent bulb lights powered by alkaline batteries, although they are not a total solution.

Formerly, the only commonly used light source for flashlights was the tungsten filament lamp. With these lamps, more power makes the filament get hotter, and its light shifts more to the visible part of the spectrum. However, lamp life decreases rapidly with increasing filament temperature.

By contrast, LED efficiency starts out high at low power levels. With LEDs, more power (extra heat) simply raises the temperature of the semiconductor junction that produces the light, which makes it less efficient and also reduces the device's operating life. The practical effect is that LEDs can operate over a wide range of light outputs and at exceedingly low power levels, and they have dramatically longer run times than conventional filament lamps--as all LED advertisements point out.

However, you need to be careful what you make of this. If you define "run time" as the duration for which there is any visible light at all coming from the unit, then yes, LED lights do indeed run for a long, long time. But if you define run time as the cutoff point at which the light intensity diminishes to only 5 or 10 percent of its initial power, well, that's different

When an LED flashlight drops to 10 percent or less of its initial output, it's not much good for spotting a raccoon in a treetop or for finding a wounded deer's eyes in the dark. But it will still let you read a map or a compass up close, or find the car key you dropped in your blind.

You also need to understand LED flashlights in general are simply not as bright (yet) as tungsten filament flashlights. Up until recently, the only commercially available white light LEDs produced up to about 1.5 lumens each, at which point they have an efficiency of only about 11 lumens per watt. In comparison, the super-pressure xenon filled tungsten lamps utilized in some high-tech flashlights have efficiencies in the 15 to 20 lumens per watt range, with lumen outputs ranging from 65 to 500 lumens.

Many LED flashlights currently on the market employ from three to five of these small white-light LEDs. You can estimate the maximum number of lumens these flashlights produce by counting the number of LEDs they use and then multiplying by 1.5. To estimate their run times at a practical light level, simply divide the watt hours stored in the batteries by the watts consumed by the LEDs.