About to pull the string on a gray Solarforce L2P (with a MF XML dropin), had some questions on the lens ....
Does the L2P come with a coated lens? Reading some posts, some think they do, others don't. Can anyone confirm?
If Solarforce doesn't ship a coated lens, looks like theres some good reviews on the KDs lens that will fit s L2P. For $2.29 for a 28mm x 2mm, a cheap upgrade to get 7-10% more OTF lumens.
But what about FlashLightLens proprietary UCL lens? They have a two 28.6mm lens, a 1.83mm and a 2.84mm thickness. Which would fit the L2P? They're quite a bit more expensive than KD's, ($5.25 & $6.25), are they worth the extra cost compared to a KD? Course I would probably get them quicker than KD being a US based vendor.
the KD lens gives green reflection just like anti-reflective coating on prescription glasses. I am sure it allows more lights to pass through, but might not be visible without instrument since our eyes doesnt perceive brightness in linear.
the ones from kd are definitely clearer than a stock glass lens..whether you can see it or not is another story..I have them on all my p60's except my 501b that it wouldn't fit in..for the 2 bucks it's worth it I think..
Some better glass I've seen reflects brown/purple.... Does 28.6 mm work with Solarforces? Cuz I ordered some 28.6, for surefire, a while back, and am still waiting.
The 28.6 from flashlightlens.com do NOT fit in the solarforce bezel. Atleast stock it wont. If you sanded it down some it probably will. I dont have them nearby but I ordered both the 26.8 and the 28.6. The 26.8 fits obviously but there is a gap in between and I feel like it compromises the waterproofness. You can stuff an O-ring on/in between but I still worry about it.
The KD 28mm lens fit perfectly. To be honest, the flashlightlens UCL do look clearer than the KD but there is no noticeable difference once light is coming out (atleast not by eye). If I could do it all over again I would just stick with the KD ones. You can get like 6 of them for the price of 2 from flashlightlens.com. The price is not worth it in my eyes unless its going on some crazy custom light and you absolutely want the "best".
BTW I have a strong feeling that the 28mm coated lens that someone is selling on CPF are from KD. If you dont want to wait, his prices arent that bad
Youre right srfreddy. sorry for the confusion. I never even tried it with the rubber "o-ring" off. I value waterproofness as I have and will drop my flashlight in puddles, etc. That o-ring creates a really nice seal.
I apologize for not fully investigating the issue though
Man, I've just checked my standard L2P lens, and... it's crystal clear :~ If I don't count reflections, I can say the lens is not there, can't really see it. So why coated lenses are better?
BTW, my ITP and Kingpower lenses are AR coated, and they don't have that bluish tint :|
There are lots of reasons to use coated lenses on flashlights but more brightness out the front isn't one of them.
Transmittance depends of the refractive indices of air and glass.
T = 4*n1*n2/(n1+n2)2 for each air-glass surface If we assume n = 1.0 for air and 1.5 for glass then T = 0.96 for the each surface and 0.96*0.96 = 0.92 for both
If we pretend that our coated glass transmits 100%, which it doesn't by the way, then there will be 8% more lumens out the front.
Would you see any difference in the brightness? [1]
Unfortunately the real world transmittance of the best coated glass is more like 0.98 for a single surface or 0.96 for both.
In this case the improvement would be only 0.96 - 0.92 = 4%
Would you see any difference in the brightness this time? [2]
The honest reason for using coated glass in flashlights is for aesthetics, not for performance. And of course there's nothing wrong with that.
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.
