Differences in Brightness Diminish with Distance

[blackscot]

I've been going back-and-forth between the Surefire G2 and G3 as a simple cost-effective handguard-mounted light on my M&P15. The 2-cell G2 is enough less in weight that I can feel the benefit in handling, so the choice comes down to whether the greater brightness of the 3-cell G3 is worth the extra load. I want to keep the gun as light and nimble as possible.

To put in context, my handguns serve as primary indoor self-defense weapons, whereas the AR is intended for longer range defense of my rural home. The light is need to identify potential targets at ranges of 50 to 100 yards in a densely wooded setting. As much light as possible is needed, while still keeping the gun compact and easily manueverable.

The incandescent G3 is rated at 105 lumens, versus the G2's 65 lumens. The difference in brightness is very apparent at very close (i.e. indoor) distances. In dark woods at around 50 yards, however, actual lighting ability becomes almost identical. I find interesting the physics of why this should be, but can't come up with a definitive explanation. Bottom line though, is that the G3 doesn't seem to be giving me much advantage.

Thoughts?

[98z28]

Can't give you the physics, but I will second your experience. I have used big incandescent Maglites and Streamlights and then switched to a 100 lumen compact light to save weight on the belt. In my experience the 100 lumen and under crowd is near worthless past 50 yards or so. If long range target identification is your goal, switching from the G2 to the G3 will not give much, if any, advantage. You are going to want a higher output (and heavier) incandescent light for that. If your choice is between the G2 and G3, I would mount the G2 and call it a day.

[exitinyourhead]

I have, I believe, a similar home situation... Heavily wooded, super dark and about a mile off of the road.

Big lights are great but, to be honest, I don't find the bigger lumen setting lights a huge advantage in the forest enviornment. I ad a g2 mounted light on my ar and while investigating something (turned out to be criters) the light started to go out on me. I had spare batteries in my vfg, but to be honest it was a pain to do in the dark and I think I would have been better off with the low light disadvantage than the squatting in the dark fumbling with batteries disadvantage. I could still see fine with the low light. I might be willing to move to a 4 cell light with a little bit lower lumen rating with even longer run time.

I switch to the G3 because of the extra battery capacity and longer run time. I was also using a plastic head g2 and the g3 had the new metal head that gives longer run times as well. I see just about as far as the woods will allow me to see with this light as compared to my rechargeable q-beam. I don't notice any change in weight from the g2 to the g3, but of course this is a short carbine in the dark and not a precision match weapon to me. I don't mind extra weight on a rifle that I only have to carry about a 1/2 mile at most, but in all honestly the felt weight difference is negligable.

I hope this helps.

[UVvis]

Not exactly the physics of it.

But the P60/P61 6V lamps use basically the same reflector as the 9v P90/P91 lamps. These aren't huge reflectors, and you are fighting several factors. First, you are using a small reflector. Reflector size and physics make a huge difference in the effectiveness of a light source. You are also taking what should be a parabola, and throwing in a filament that is wide, and not an infinitesimally small dot. So the reflector has a certain amount of slop built in, hence the stippled finish, which isn't the best reflective surface. Plus with surefire, you are exchanging a smooth beam, for a long casting uneven beam, with rings and artifacts in it.

Next, you aren't putting out a huge difference in light. Going by the ratings you have maybe a 40 lumen difference, not much, especially at distance. Granted the light going out is focused, you are really looking at the light coming back that is scattered off the target. This is a form of EM radiation, so you have the same exposure/distance effect going on. So if you are twice as far, you are getting one fourth the dose. Compound this with less light getting to the target at distance, and you get even less back.

So basically, for seeing things farther away with a light at night, more lumens and larger reflectors are the way to go. Just throwing more lumens at it doesn't always help (think 100watt light bulb, unfocused, and 800ish lumens), nor does a larger reflector (think mag-lite).

So unless you are planning to go with the 9V turboheads from Surefire, I'd stick to the 6V light for size/weight reasons.

[RD62]

Kind of what I was gonna say too. Go to a Turbohead or stay with the G2.

-RD62

[uspopo]

I would go with the G2Led and if you need more brightness you can always go for the aftermarket P60 Cree assemblies with 200+ lumens. The Chinese lamps over rate their lamp outputs by a lot but you are still getting a lot of output at the expense of running time (approx. 1.5 hours on a set of CR123s). I am patiently waiting for SF to release their 120L P61Led head.

Stan

[blackscot]

Thanks for the replies folks.

Seems to confirm my leaning toward going with the G2 on the AR. The G3 will be assigned as hand-held house light.