rifle mounted torch

[fenring]

It is true that manufacturers have gone lumen mad. It's the Feet Per Second of the airgun world, or the megapixels of the camera world - same thing of "more is better."

The longest throwing LED torches out there are not generally high lumen models - what's important is Lux or light intensity = how much light is hitting a small area or target, as opposed to how much is spewing out the front of the torch and in all directions.

Makers bamboozle with claims of 1000 lumens or more (most often exaggerated!) which doesn't tell you much about how far the torch projects or how the beam is collimated.

The longest throwers you can buy are still using the small Cree XR-E emitter and putting out 200 - 275 lumens but the beam is collimated tightly so you get the bright spot to light up your target. The reason the XR-E is being used as opposed to the much more powerful (and fuel hungry...) XM-L is that by default the XR-E (or as it's often known, the "R2" ) emits a more tightly focused stream of light. Combine this with one of several ways of collimating the beam - namely a deep, smooth reflector with the right sort of parabola, an aspheric lens as per cj7's light or a TIR optic as used in the LED Lenser P7, or the recoil lens setup found on the Ultrafire 008 light and Pelican torches - and you get an intense beam.

Makers are trying to make throwers using the XM-L but the lights are bulkier by necessity, needing a bigger head and lens and often using two 18650 batteries to get a decent runtime. The Lux figures are not up there with the best XR-E throwers despite three or more times the lumens coming out the front.

The other thing out there is the Laser Designator which, instead of trying to focus an LED light stream into a tight spot, uses a focusable or rather DE-focusable laser beam. The result is a very tight and intense spot of light (generally green) that goes a long way but is next to useless for searching for game.

[cj7hawk]

Fenring.

Yes, you're right about the searching problem. Searching the field through the 2 degree beam is a little like searching the field through the riflescope, though I can actually remove the collimator and get a 6 degree beam or wind it out to about 40 degrees for just wandering about.

But the intent wasn't so much to make a lightweight torch for pointing around, but rather one fixed to the rifle so that once you spot eyeshine, you can identify and take the shot in one motion. And originally I was researching infrared illuminators and just happened to put several pieces of what I was playing with together with my normal torch so I could get an idea of what was happening to the beam with visible light. The effect was unexpected. The lens itself is actually optimised for IR, but then the light was going through it the wrong way, so that worked out OK.

Well spotted, yes, an aspheric lens is the first part of the torch, to collect as much light from the element as possible. Then I use a 3:1 concentrator to take the beam from 6 degrees to 2 degrees. Basically a small telescope in reverse.

KJD -

A 200 lumen torch? It would be brighter I find that I get a lot of light loss each time I increase the concentration, but I also get the same amount of light on the target at a further distance... The base torch by itself easily goes 100m... Very visible. You'll see colour at that distance. When I concentrate it threefold, I can get it to go well over 200m, but at 300m, it's not as bright as the torch is un-concentrated at 100m. Does that make sense?

But the other problem is more light = less battery time... Personally, I hate my 500 lumen torch, because it only lasts 15 minutes and is heavy. Also, I need to get the entire amount of light out of a single LED element - not three or four.

Anyway, I don't mind sharing a little research for those who want to follow - The base torch is just a "zoom torch" - They cost about $10 ( just checked on Ebay ) and they do come in 200 lumens now or so it seems - So I'll get one of the 200 lumen models and set it up for an experiment As a cheap, high quality shooting/hunting torch, the zoom cree's are probably the best I have ever tried...

Regards
David

[fenring]

The XR-E or "R2" emitter is the way to go if you want a tightly collimated beam. By default it emits the tightest stream of light out of the emitter. The XP-G or "R5" can produce more lumens, but has a larger hotspot by default and is harder to focus. The XM-L can put out around 1000 lumens but once again, is harder to focus and needs a bigger lens to do it.

The method I use quite often, is to use a regular torch with reflector, on a lanyard around my neck to pick up eyeshine. Then I can take it from there with the rifle mounted spot beam.

Edited to add - many of the aspheric lights use glass lenses of poor quality, or plastic lenses so you lose a fair bit of efficiency.

You can make your own fixed aspheric lens light by using one of the many P60 sized torches (like the Solarforce L2) and getting a cheap glass aspheric lens from Deal Extreme, the XR-E dropin and a smooth reflector. You just replace the flat glass lens with the aspheric, and play around with the spacing until you get that tight, square hotspot.

I've got one set up with a RED emitter. The red emitters can't be driven as hard, so that's a limiting factor to how bright they can be. But boy do they make eyes light up!