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Thanks for your comments DW. To verify, my measurements are taken using a meter that reads out in either lux or footcandles. I measure from two feet and am careful to read the beam's brightest point (which can be tricky, depending on the beam characteristics, despite the dome diffuser on the meter). If I increased the distance to, say, four feet the reading would drop by a factor of four because of the inverse square law, so that's perhaps where the confusion on the reported value stems from.
For consistency among our published tests I've used the same meter for each flashlight article done for BPL, and inherited both the light meter and the two-foot measurement distance from the reviews done by others before me. I don't have a light source "standard" to verify the meter between tests but it does allow me to zero it. I'm confident the BPL test results can be compared to one another, with the caveat that battery variability cannot be ruled out.
Flashlight makers seem to primarily rate their products in lumens but I don't have the rather specialized equipment required to test that parameter. If they reported lux they'd have to use a standard measurment distance to enable comparison among brands, and that's unlikely. What we, the consumer can do is use the given lumen values to compare models within a brand's line, but I'd be leery about comparing the value among brands. That would be akin to comparing sleeping temperature ratings across brands (territory over which I fear to travel).
Cheers,
Rick
Edited by halfturbo on 02/03/2010 10:26:59 MST.
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