In , Frank wrote in part:

SNIP previously quoted material

Yes, I would look for the led and look for watt, candlepower or lumen
output.

Watts are a unit of power consumption - and that can be either actual
(either taken from the batteires or delivered to the LED, 2 different
things) or the maximum that the LED is allowed to have dumped into it.
(How much extra by driver circuitry or dropping resistors varies widely.)

Since this means there are already three different things that wattage
can refer to, and efficiency of LEDs varies widely, wattage has only
"fair" correlation to light output.

Candela is the intensity of the beam, and roughly means "beam
candlepower". This refers to intensity of a beam in the distance, and
decreasing area of the beam covered gets this to increase when lumens are
unchaged.

Lumens may be what the LED is rated to produce, and in that case is
often at some specific high amount of current, and also in that case is
usually specified at some non-real-world level of cooling the LED, either
cooling its heatsinkable surface to 25 degrees C (77 degrees F) or
worse-still cooling the "junction" (within the LED's chip) to 25 degrees C
(77 degrees F).


I bought a 12 led lantern for my wife's use during power
failures and it does not even give off enough light to read by. She
bought me one with 20 leds focused in one direction and you can read by
it. I have several other led lights and, as I said, they are adequate
for close work. What I really like about led's is that they get much
more effective power out of a battery.

My main use is hunting and just this week I was out at 5am in an area I
was somewhat familiar with but needed a light to find the public stand
and the Lowes light was great illuminating trail markers 200 yards away.

I do agree that LEDs tend to be better for flashlights than incandescent
lamps. Modern LEDs are finally mostly more efficient than incandescents,
many times by a substantial difference, and - unlike incandescents - they
do not lose energy efficiency much (or at all) when power input is
reduced.

- Don Klipstein )