Coated Lens for a Solarforce L2P?

I got a huge difference in my lights.

OK, the original lens was filthy. I reckon that for my lights I'd not get more of a boost any other way for $3.

But if you keep them clean the difference is a lot less. I still got a visible difference even with a freshly cleaned plain glass lens.

I got 870 lumens at switch-on with a new coated lens compared to 796 with a (dirty) plain glass lens that came with the light. Once I'd cleaned the lens and put it back, it still gave a lot less than the coated one did. I forgot to record the numbers on a spreadsheet but there is a thread around here saying what the results were.

http://budgetlightforum.cz.cc/node/1026 Thanks Don, there's your lumens recorded in that thread, with some other users that are even greater. I would have never thought coated lens would make any difference, unlike camera lens or eyeglasses. But light meters don't lie.

But angusinalberta brings up a good point ... "Would you see any difference in the brightness?" Really, I dunno. But for $2, I've spent more on tethers or gitd o rings that have no effect of lumens

I have a suggestion for measuring the transmitance of glass lenses that will keep all confounding variables to a minimum. I don't have any coated glass here to do the experiment myself or I would.

Place the lens that's to be tested over the light meter instead of the flashlight.
This probably requires a black cover over the light sensor with a hole a bit smaller than the lens cut in it.

Shine a steady light on the meter and record the following readings;
a) no lens over the meter
b) uncoated lens over the meter
c) coated lens over the meter

Repeat 5-10 times and calculate averages.

Transmittance of the uncoated lens = bave ÷ aave * 100
Transmittance of the coated lens = cave ÷ aave * 100

Prediction: no more than 4% to 5% difference between the two results or I eat my hat.

Cheers,
Angus

The Flashlightlens.com UCL's are something like 99.2% transmittance, IIRC. a

Be an interesting test, and I agree would most liklely result in a 4-5% difference, probably much lower. But it would not be a very practical test, as it would only measure the translucence of the glass alone, and not the overall translucence of the glass combined with the compounded refraction of the reflector to glass. Buried in the original thread is an interesting wiki link to thin film interference (http://en.wikipedia.org/wiki/Thin-film_interference). Of particular note in this article is the phase shifts on what is termed constuctive vs destructive interferences - which would not be measured by your scenerio.

um, I think. :-)

That's in agreement with wikipedia


Reflectance of 0.5% implies transmittance of 99.5%

0.9952 = 99.0%

I wonder if DX lenses perform as well.
Worthy of a comparison test?

Cheers,
Angus

Not at all, it is a very practical test, in that it tests one variable, the effectiveness of the anti-reflection coating. All other things, lamp-meter position in particular, remain exactly the same. In science it is always preferable to change one, and only one, variable at a time.

Another excellent wiki article is at http://en.wikipedia.org/wiki/Anti-reflective_coating
It explains how the transmission of light through an air-glass interface is enhanced by destructive interference of the light that would normally have been reflected if the quarter wave thick coating were absent.
Hope that last sentence makes sense to you. It's past my bedtime.

Cheers,
Angus

Actually, it does. But of course enhanced by the six pack of excellent local micro-brews been thoroughly enjoying tonight.

Tomorrow morn will probably have no idea what you, or I, were discussing.

Cheers my friend, Tom

My glass needs replacing .I like my light . I’m tired of garbage .I want more output too .4 more good reasons to buy good A/R glass…

Don ...easiest answer is quit smoking ..think of the time you'll save cleaning .AND Your lights and your teeth will be brighter .

Even the dog has more sense than to stand downwind from a campfire .

Sorry guys for bringing back a deadthread but for those of us who are interested in upgrading our lights I want people to know that KD is still selling the AR lenses and I just bought a few of them (6) for testing purposes. I mean having a Bushwhacked P60 Drop in deserves a nice AR lens right? Right! I can post the link to the 28mm ones if anyone else is interested in one for their light. Mine happens to be a Solarforce L2 and, from what I have gathered, the KD 28mm fits nicely.

The real gains come when the light is hot rodded. And the best gains come from the flashlightlens.com UCL and UCLp.

I don’t know if the KD lens give any appreciable boost in output, but they sure look nice, and to be honest that’s the only reason why I bought them. :bigsmile:

I think there is a thread here on blf that compares different lenses for p60 format, the light gained using a KD lens was around 5-6% the lenses from flashlightlens were even better.

I wasnt really looking for a huge boost in output though im sure anythings better than what it came with. also I wanted the look as well! It sure looks sexy with an AR glass.

Let us know what you think. I also ordered some lenses from KD. I ordered the ones that go for $3.10 rather than the ones for $2.9x. The KD website said the more expensive were the ones to get so I believed them. I don’t like glass with tint so I
may be disappointed, expecially if I can’t see a difference in OTF lumens.

Unfortunately, KD even with the registered air mail is terribly slow. I order from other Hong Kong companies and receive their stuff in 8 days. But KD has had my order for 13 days and it just left HK and I still can’t track it.

Im not sure if i will be able to tell. My Bushwacked LED should be in before the lens so hopefully i can get some output shots up and some lux readings from my phone lux meter. I will do a stock glass kd glass and no glass reading. Also can you send the link for the lens you bought? Thanks

Here is the link for the ones I bought. http://www.kaidomain.com/product/details.S004329

I bought those exact ones! I just bought 6 of them…

I had planned to buy these http://www.kaidomain.com/product/details.S021820
which I thought were the ones everyone had been talking about in these forums. Then the slightly more expensive ones ($3.10) showed up on their website with the info on their page that said these were the best so I ordered them instead.

For what it’s worth, I ordered two different 28mmx2mm lens from KD a little over a year ago, and one type had a “green” AR coating while the other had a “purple” AR coating. Both types were flawless; they perfectly matched the diameter and thickness of the stock lens, and I couldnt perceive any tint shift between the two. I’ll try to find some links to them tonight.