Polycarbonate Lens? Why call it a lens at all?

greenlight

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They could have easily included a glass 'lens' to supplement their poly one. Then there would be no discussion of whether they were trying to save a buck.
 

Oddjob

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They could have easily included a glass 'lens' to supplement their poly one. Then there would be no discussion of whether they were trying to save a buck.

+1. And I think extra O-rings should be mandatory for a light like this especially when other sub $50.00 light come with them.
 
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SunnyQueensland

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Flashlightlens.com is where I got mine. I ordered the ones listed for the HDS EDC. http://www.flashlightlens.com/appchart.htm My lightbox shows an increase of 400 lux with the glass lens over the plastic one.
I measure the O-ring OD to be 22.5mm.

Many thanks... I have tried to track down this info everywhere. I can't have a 'plastic' window on my flashlight. :ironic:
 

yaesumofo

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I thought about this for about a second. The real cost of a UCL is about $1.00 to $2.00 in the quantities we are talking about. The Hi quality Polycarbonite lens may cost 1/2 of that maybe even a 1/4. what is the difference between .50 cents and

I think it was to cut cost.
$1.00 to $2.00? On a $150.00 flashlight the cost of the "lens" is very minor. I don't beleive they did it to reduce costs (the same lens can be found on the HDS EDC flashlights) The reason for using the Ploycarbonite lens is to add durability to the light. The Polycarb resists dammage and cracking under far more extreeme pressure and impact than any glass or crystal lenses.
For use in situations where the light will be subject to high force levels where the probability of being dropped is high, in conditions where the light will be subject to dropping throwing and high falls. The polycarbonite front glass is the best choice.

I agree that the use of saphire is not optimal for light transmission. It is highly scratch resistant. I have repalced the saphire "lenses" On my PD's to UCL's as well (I have carefully put the saphire peices away. The AR coating is delicate and the lenses are very pricey. The PD with a UCL has a higher light output. Can you see a difference? NO. But it is measureable.
Yaesumofo
 

ensile

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What we do not often know about plastic lenses is what the composition of the plastic is. I am wearing plastic lensed glasses that are very clear. Why not a plastic lensed flashlight that is equal, or almost equal to clarity of a glass lens, UCL, or borofloat.

Bill

then cost would be upped, more rings would appear and if it's just a loss of lux they would compensate with driving the led a tad hotter.

DW, this is what research and development is for.
 

ensile

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Many thanks... I have tried to track down this info everywhere. I can't have a 'plastic' window on my flashlight. :ironic:

it would more than likely be milspec high impact polycarbonate, what most synthetic materials are made from which have to sustain sharp knocks or dull pressures, but still resist splitting and cracking whilst retaining its original shape.

in orther words, it's not melted down tic-tac packets
 

wakibaki

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Can you see a difference? NO.

A difference that makes no difference is no difference at all.

Considering that you can get the overnight release of a new bin LED with a jump of 10 or 20 lumens, the influence of the lens (window, photon port) is trivial.

The thing about words is, they just mean what people use them to mean, regardless of any rules about right and wrong, and if you want to be understood you just have to use the words most people use.

+10 lumens? Now that's a difference.

w
 

Oddjob

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I remember reading that 4sevens took reading through a UCL and Saphire Crytal and found a 10% reduction in the Saphire crystal. Does that mean 50 lumens would be reduced to 45 lumens? I think anybody would be hard pressed to differentiate 50 and 45 side by side.
 

GarageBoy

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It's anondized grey, so it's Aluminum
Yes, 10% difference with Sapphire, but why bother selecting bins, optimizing power regulation, only to have your window take it away
 

ElectronGuru

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Why is it called a Lens when used in flashlights?
It is a front glass. It's job is maintaining a seal against water and to protect the emitter reflector optic from dust and debris. It is generally not an optical component or part of a compound lens of any type.

What do you guys think?


Short answer: we call them 'lenses' for the same reason we call them 'flashlights', because it used to make sense.

Long answer: 'portable light emitters' originally had such weak batteries they didn't even have on/off switches, just momentary activation. Using it, you just flashed it for a few seconds at a time trying to conserve energy. In the US at least, the name flashlight was coined and stuck, despite efforts to break it loose. So to with the lens. Have a look at this early model, particularly the front end. Batteries to weak to last were also to weak to throw [light]. To get the most out of limited lumens, a magnifying glass was placed in front of the bulb:


1899_Eveready_flashlight.jpg



ElectronGuru

(this is my first ever post, feedback welcome)
 

Barbarin

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As manufacturer I can tell you that we choosed polycarbonate because of to the kind of use our lights do have usually. Our customers preffer having a scratched or even dented polycarbonate, and change it whenever they want to or they fit, than a broken one on the worse moment and no time or way to replace it. For extreme uses PC is the way to go, unless you are using high power incans, which will melt it.
 

L.E.D.

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Some also worry about the gradual yellowing of polycarbonate "lenses" under exposure to UV. Are their worries unfounded nitpicking, or would leaving a light with a poly lens under the sun for a few days really show yellowing?
 
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ElectronGuru

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Some also worry about the gradual yellowing of polycarbonate "lenses" under exposure to UV. Are their worries unfounded nitpicking, or would leaving a light with a poly lens under the sun for a few days really show yellowing?

I don't know if quality varies (optical grade?), but I've had the very same set of polycarbonate lenses in my eyeglasses for going on 10 years now. Thats 16 hours a day for 3000+ days straight: indoors, outdoors, hot, cold, hostile and not. There is not the slightest degree of color variation and nary a scratch. I for one am sold.
 

Christexan

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Realize that there are different grades of polycarbonate, and as well, most eyeglass lenses (true lenses) are treated to one or more of many treatments based on their intended usage.
At the most basic, all polycarb lenses that I'm aware of are UV protected... the lens provides UV protection for the eye, but the material itself is also stabilized, so no yellowing over time (in reasonable timeframes). Unless you go totally cheap, the lenses are typically also scratch-resistant coated, as poly eyeglass lenses DO scratch easily if uncoated (buy a cheap pair of poly reading glasses at a drug store and rub a little bit of anything on them and you'll see). And of course you can add additional anti-glare, anti-reflection, and other treatments to them as desired.
Compared to the $0.25 "window" on a flashlight, which likely has NONE of the above treatments, and it will yellow with excess UV (outside in daytime), it will easily scratch, etc. But as mentioned, you could probably buy a 10-pack of them for a buck or two to replace as needed, compared to eyeglass lenses costs. The reason eyeglass lenses cost so much isn't the polycarb itself (again, drugstore poly lens reading glasses are like $10 or whatever total), it's all the treatments done to make them more durable and long lasting and enjoyable for all day every day wear.

Spaceshuttle windows are made of polycarb also, obviously with extensive treatments done to them for heat, UV, radiation, scratch resistance, etc.
 

Barbarin

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Most of the lamps you can find on street lighting are made from polycarbonate, same the headlights protections you can find on many cars. Some of them stand during a lifetime even having behind them high power HID bulbs. I think the problem with yellowing polycarbonates is with low quality ones, as the quality ones have additives to protect them.

Javier
 
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