100 m throw Photon Freedom

liquidsunshine

liquidsunshine

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Hi everyone!

Not sure if this is the right forum - moderator, please move if appropriate, thanks!

I had two items lying on my table recently that suddenly yelled at me "use us together!" Now the result is not strictly speaking a Photon Freedom with 100 metres throw - nonetheless those of you who carry some survival gear may actually have said long reach photon in their pocket without knowing.

It's simple: Hold a credit card sized fresnel lens - which is basically only a foil no bigger than a card and pretty cheap - in front of your Photon, or whatever other single light source flashlight you may have. To add stability, rest the hand holding the Photon on the lower arm that holds the lens. Line up light and lens, shine the light vertically onto the lens surface, and vary the distance to get the beam you want. For my lens, the best distance between light and lens was about 15 centimetres.

You can quite easily adjust te tightness of the beam within a surprising range. In a residential area with quite a bit of light pollution, I could see the Photon Freedom beam on objects about 6 metres away without the lens. In the "freelens superspot setting" [TM] I could easily see the bigger branches on a tree that was about 70 metres away under the same conditions! In total darkness that would be 100 metres or more.

Now this setup is certainly not very handy and requires both hands, BUT the lens is easy to carry and a multi use item, and if you want to signal someone at a big distance of whom you know the approximate location - scanning the horizon in one particular direction, aiming at SAR aircraft etc. - it could well increase your chances significantly.

The visibility of the light for another person would be drastically increased if aimed correctly. I'd LOVE to see a test done on this - Doug Ritter, in case you're reading here: If you're ever doing land-land or land-air visibility tests with lights again, could you please also test this setup?

Worth mentioning: The beam is so clear cut that if the air is not totally clear, you can see its angle and where it is going easily, allowing you to adjust the width according to what you want to do, and aim it even if the target is too far away to actually make the beam visible to you on objects.

If anyone tries with other lights or has other ideas arond this it would be cool to hear from you.

Cheers,

Matthias
 
e2x2e

e2x2e

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Really? I've tried this with other lights and it never seemed to do anything! I'll try again though.

Edit: Just tried it with my NDI and a Fresnel lens. It really works! I had to hold the lens about two feet away, and on the lowest setting the beam was really concentrated.
 
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matrixshaman

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Very cool find - I think I've got one of those somewhere but I don't know where right off hand. I've got a big 8x10" one too - never really thought about using one to focus a light. I think I'll stock up on a couple of the credit card ones. Where did you find these?
 
Gunner12

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It should work the same as a lens. IIRC a lens is more efficient but a fresnel lens is much thinner.

I've tried just normal lenses with some of my lights and it works pretty well. But the beam is not that pretty due to the reflector.
 
Blue72

Blue72

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I did something similar

I took a aspheric lens from my minimag and put it on the ARC AAA and I was able to light objects over 200 feet away
 
Crenshaw

Crenshaw

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where can i find this throw enhancer?

thanks!

Crenshaw
 
Sgt. LED

Sgt. LED

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Fresnel lenses of all types come up on search engines.

Before you look - know the distance from the lens to the emitter.
I think magnification depends on how closly the rings are spaced?
 
Gunner12

Gunner12

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I think how closely the rings are spaced is just how flat the lens is. The curves on each ring(and all the rings total) determines the focal point.

I'm not sure though.
 
F

flashfan

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Liquidsunshine, thanks for the tip! This is so cool.

I have a freebie, credit card-sized magnifying "glass" (plastic actually) with rings around the center point. Don't know if this can be considered a fresnel lens or something even close, but it's pretty amazing.

It really concentrates and extends the reach of the light. Tried a variety of different incan and LED lights, and found that it seems to work much like a movie projector.

Using my L2, the lens projected onto the wall, a very clear "picture" of the L2's textured reflector and the "glowing" square-shaped LED die in the middle. (Same thing you see reflected when shining a light on the lens of a pair of glasses.)

Tried to obscure the flashlight detail and obtain a nice beam by sticking a couple layers of "diffusing" scotch tape over the end of the flashlight. And LOL, instead of a smooth beam, the magnifying glass projected a very clear picture of the tape over the reflector and LED.
 
liquidsunshine

liquidsunshine

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You should be able to find them in many places that sell glasses - they are used as magnifying glasses for reading. Should only be a couple of dollars or so. They also have HUGE ones there!

Of course it works with a normal lens too - but I wouldn't want to EDC a normal lens of that size, which would be quite hefty!

Probably it will work best (in terms of even beam) with lights that don't have a reflector. For me, Photon Freedom + fresnel credit card lens is a great combination - for very rare use, but at almost no extra weight or bulk.

My fresnel is plastic too. Glass and a normal lens would be more efficient, but the plastic fresnel is more satisfactory to me - still many times more throw than the Photon has without.

It indeed IS a projector - what you are projecting is the shape of the light source, that is, of the LED emitter. As in LED's that is a reasonably even area, it's useful with lenses - an incandescent bulb would give you the picture of the filament, more or less. You can avoid to have the light source projecte too clearly by slightly being out of focus - which is perfectly reasonable and actually done in many lights.

Btw, if you have an incan, and cover the front of the light so that only light from the far side of the reflector can come out, e.g. with a piece of cardboard that has a hole (experiment with diameter), you can see the projection of the filament very clearly. The only reason why you don't normally see it is that the beam consists of a huge number of projections of the filament that are all overlapping partially, creating a more or less even beam appearance - depending on the reflector's design and quality. Welcome to the world of optical design :)

If you actually want to project something it has to be close to the focal point of the system; in the system discussed here, for an ideally concentrated beam, that means as close to the light source as you can get.

The article of Andrew Davidson is excellent, I might as well just have posted the link here... DARN now I want one of the giant ones! Oh-oh... a new obsession is born.

Anyone ever tried to use a giant one as a camping stove...???

Cheers,

Matthias
 
liquidsunshine

liquidsunshine

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...but you are not talking of using a flashlight and a fresnel for that, right?! :)

Cheers,

Matthias
 
8

83Venture

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Just tried it with a Photon covert and LF2, it works. You can find these at most book stores and in the book sections in Kmarts/Walmarts etc. Sometimes in the office supply sections. Usually only a couple dollars.
 
Crenshaw

Crenshaw

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ohh, these are those, pocket/wallet, whatever, magnifier thingies right?

Crenshaw
 
Sub_Umbra

Sub_Umbra

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Bravo liquidsunshine,

I have card sized plastic fresnels and PFs stashed in numorous kits. Daddy like!
 

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