As an example, assume you have a 5mW laser and a 1W LED light on your pistol. The laser has all of its photons in a super small column that does not spread out much from you pistol out to 100 yards. The LED light has a much lower intensity than the laser but gives off 200 times more photons. Since the light spreads out rapidly, you can't see squat at 100 yards with it.
The laser has a massive intensity ie.; high candella value but very few lumens. You can illuminate a super small area (say 1/4" diameter) at a very long distance, but can't see squat 2" away from the laser dot.
Conversely, the light has substantial lumens but lower candella. You can see most everything in a decent sized room but not much further out.
So to your question, If you want to aim, quickly target, or blind the opposition (permantly or temp) it's pure intensity (candella) delivered on-target. If you want to be able to see a wide area quickly then it's lumens.
Does that help any?
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Last edited by TXAZ; January 26, 2013 at 05:49 PM.