Thanks,
We tend to post at same time 
So for those KD and similar China stuff AR lenses we mostly use here. Did you tried and what coating do they have?
Never tried them. I would assume they are VIS AR coatings if they are made for flashlights.
Probably much worse quality though than the type of stuff you get from edmund optics or flashlightlens.com.
It is certainly possible that a crappy AR coated glass lens has worse transmission than a high quality non-coated acrylic one, you never know with that stuff from china.
This is why I try to get my stuff from more reliable sources like high end optics manufacturers or mountain electronics and places like that.
My light has this: FlashlightLens.com - Your source for high quality glass and acrylic flashlight lenses. - Flashlightlens.com - Online Store
Why?
Because they are known to be good and they offer custom cut sizes without being really expensive. I also thought they were robust, but…
Edmundoptics is serious manufacturer while flashlightlens is distributor of quality stuff? Shipping is something that will kill most of users that are not from USA.
So acrylic lenses can have 97% of transmittance and they are probably more durable than glass one.
My acrylic lenses I use as preccolimator in aspherics seems to have 100% of light transmittance without AR coating??? How I stupidly concluded that? 
Cause without them or with them I have same result on lux meter(with them I have 100% larger beam of course)
And sometimes they are even scratched but it seems that they do not loose on performance because of that.
I want to say acrylic or plexiglass(I did not tried plexiglass yet) is worth a try weather for plano plano or plano convex?
And that middle thing on this The Driver build is something similar that MEM want to try before he disappeared. He told me he can find a way to fit RA on reflector lights and enhance a throw.
Thanks Dale, that clarifies things, feels strange though, so to reduce spill people could stick something on the GT right in front of the led
Well The Driver scratch my input on making a lens yourself then. Besides I can understand that with this build you want the best you can get
Are you talking about some other flashlight? Not the maxabeam you just built, right?
The minimum order quantity for a custom size lens is 100, so even though each lens might be cheap it ends up costing hundreds or thousands of dollars.
A custom 100mm lens at $.15 per mm is $15, but with a MOQ of 100 it becomes $1500…
Cheaper to buy something from edmund optics TBH.
That MOQ is for the glass lens I think. I’ve ordered a couple of the UCLp in different custom sizes.
OOOH I see, didn’t see that thanks
It only lists two acrylic options though, under the custom sizes category…
Yes, flashlightlens.com is a distributor of quality stuff. They have been around since 2002 and only sell lenses for flashlights. They, as far as I know, bascially invented the concept of the “UCL” (ultra clear lens) for flashlights. They also sell borosilicate lenses, which can tolerate high temperatures. Many people on CPF used these for hotwire lights for many years.
Well yes and no. They are a bit more durable because they don’t shatter, but my lens cracked in this light. It was my first very big lens. Before I had UCLp lenses up to 75mm.
Your light meter might not detect small differences correctly.
The reason is probably something else though.
The precollimator corrects for the imperfect shape of the main lens. Normally you would loose 7-10% of throw because of the pre-collimator. but you don’t loose anything. This means that the pre-collimator is “making it easier” for the lens by making the LED “seem bigger”. I hope you understand what I am trying to say.
Well glass will always be better if it is high quality. So you just need to test I guess.
Not quite, it is your guess ;).
I’m intrigued.
A reflecting collar could work, I think. The increase in luminance would not be as dramatic as when it’s used in a lens light though. In a lens light ~70% of the light is available to “recycle”, but only ~30% is available in a reflector light.
I am another one thats just say Wow…
Really nice build
Well 30% in 1,5milion reflector is a lot 
around 500kcd
I’m actually thinking maybe reflector is the way to go for ultimate throw.
Lenses have a lot of chromatic aberration which almost certainly reduces the lux.
The problem is that to get the best throw, the LED intensity needs to be extremely high, and the wavien collar does massive improvements to that, over 2x.
In order to use the collar with a reflector it would need to be a recoil reflector, not a forward facing one like in normal flashlights.
Then the problem becomes the LED + collar blocking a bunch of light from the center, which is the most intense light, thanks to the collar in the first place.
.
The solution:
Off axis parabolic mirror!
-no chromatic aberration
-no blockage of light in the middle
-can use a collar to get over 2x LED intensity
.
Problem is that it would cost several thousand dollars 
but still, I’m pretty sure this is the BEST method of getting maximum throw per diameter (with an unlimited budget).
Thoughts?
In theory yes, but think about it again. You would be blocking the reflected light of the reflector.
The Maxabeam Reflector used here has a 40mm “dead” hole, when used with LEDs. So that is the maximum diameter which the “reflecting collar” (this name doesn’t really make sense here, it doesn’t go around the LED) could have. The distance of the reflecting collar will then determine, how much light it collects from the LED. It would need to be just far enough away so that the light of the LED can hit even the outer edges of the reflector.
Of course most of the spill light will pass through the reflected light of the reflector and will thus never hit the “reflecting collar”. So in reality there is hardly any gain to be had here, maybe 5-10%.
Enderman’s idea to use an off-axis (main) reflector would work much better because more light can be collected without blocking the beam, but it will never be perfect and the light would probably look rather weird.
MEM from this form(inventor of that wavien collar or RA- reflective aperture how he calls it) wanted to try different approach to led reflectors and he called that RRR…
So i will quote him ” “The Recoil Recycled Reflector. Fitting? It is essentially a recoil format, in that the LED directs light directly into a “barrier” that “recoils” the energy back through the phosphor, “recycling” output back out to the “reflector” “
And you are probably right with this mirror idea cause he wanted to fit as I managed to see flat smaller diameter mirror. So his idea should really work but centering the mirror to the right distance to led will be nightmare.
Edit: He mentioned that XPG3 would be most suitable emitter for that because of all unused phosphor surface!
It is sad MEM vanished, a week after he pmmed me how sad it is when people vanish
The best method also takes effort and cost into consideration IMHO. Half the price 10% less good = better
I spent $400 on batteries for a flashlight, does it sound like I settle for 10% less good?
I think a spherical reflector could be designed to capture all of the spill light for most all reflectors with typical width-to-height ratios.
Below are some rough to-scale sketches of what I am thinking.
The top reflector is a C8 reflector with 38mm active diameter, 32mm height, and ~12mm dead hole diameter. The bottom is a convoy L2 reflector, which is a bit more relatively deep, with 54mm active diameter, 50mm height, and 16mm dead hole diameter.
Let’s constrain the diameter of the spherical reflector section to be the same as the dead hole, so no light from the reflector is blocked. Then the optimal position for the spherical reflector would be as in the sketches, to just allow the LED light to reach the edges of the reflector, but capture all of the would-be spill light. Then the radius of curvature of the spherical reflector is chosen to be the same as the distance separating the LED and spherical reflector, roughly 12 and 18mm in these examples. (I’m approximating the LED as a point in these sketches for simplicity, but I don’t think a finite size LED would completely change the picture.)
I think this makes sense. Have I got something wrong? :sunglasses:
EasyB you’re correct, this is basically the reverse of a wavien collar+lens, however there are several reasons why this would be worse.
1) the main optic diameter will remain large, since the spherical reflector takes light from the middle rather than the sides.
Something I think is very important is not just getting high lux, but getting high lux per diameter of optic.
Anyone can take a big lens or reflector and put it in front of an LED to get big numbers, but the impressive thing is getting BIGGER numbers with the same diameter, or similar numbers with a smaller diameter.
2) The collar the way you drew it would only collect very little light, resulting in an intensity increase much less than 2.2x like the wavien collar does.
In order for it to be equivalent to the wavien collar, your spherical reflector would need to be collecting 120 degrees, and your main reflector would need to be much flatter and collect 30 degrees on either side.
Again, this would result in a large diameter of main optic.
3) You can see in the drawing that the parts of the reflector near the bottom are still very close to the LED.
This will be contributing to a big corona and less-sharp spot projection.
With a lens, all the surface where the light hits is farther away, giving a tighter beam and smaller spot.
What difference does a “sharp” spot make? More candela is always more candela. And the collar is doing exactly what you say - improve candela for a given optic size.
@easyb
That looks good. I guess I had an error in my thinking.
Just so you guys know - I am not actually interested in this for this light. I actually want the little bit of dark spill light it produces.