I cant get dedomed LED to focus perfectly!

I can perfectly focus all my domed LEDs, but the dedomed ones always leave blue/orangeish squares/lines around the hotspot!
it kinda looks like this:

I am not able to post beamshots because my phone camera just registers everything as a white dot.

the domed ones look nice and perfect like this:

Emitter in question: xpg2
Lens used: 44mm Aspheric
I also covered around the emitter with black tape, I did not cover the metal around it however. In addition, the host holding the lens also has black tape, so there are minimal internal reflections.

  • Are the dots on your die in focus?
  • What 44mm Aspheric is it?

Those look more like aberrations than a focus problem. Optical aberration - Wikipedia

EDIT: but I have no idea why it’s happening w/ the dedomed XP-G2 and not the domed one. Does the dedomed emitter act normal in a reflector?

Light is perfect in a reflector. Perfectly round. But once I switch to the 44mm lens, those squares start to appear. I have 2 xpg2 dedomed and they both have funny squares. I also have 2 44mm Lens and they both show squares.
I am not able to focus the till I see the dots on the LED.
Maybe both my lens just sucks… hmmm

EDIT: I FIGURED IT OUT! I had some small plastic lens and I tried using that and BAM! goodness gracious! the perfect square!!! I guess my glass lens is grabage. D: any suggestions on quality glass lens? I got mine on ebay for like $2.50 USD

44mm Lens - EBAY

I guess domed emitters are easier to focus with crappy lens

Mjêh, a lot of the cheap glass lenses are just not as well shaped as their PMMA brothers… :frowning:

Is there anything i should look for (keywords?) I don’t know if i will just buy another crappy one again… So is PMMA better than glass?!

PMMA lenses have been better for me than glass lenses. But then I never bought expensive ones. So maybe I should say that as far as budget lenses go, PMMA has been better for me.

I guess PMMA is easier to work with just because it is plastic? Do you know where I can get 40+mm PMMA lens? They seem to all be glass!

To clarify:

  • Are the blurry pictures in the OP actual pictures of what’s going on? Or are they simply pictures you found which look vaguely like what’s happening?
  • What distance are the pictures taken at?

The pictures make it look pretty extreme, which isn’t normal. What is normal is to have a bit of a colored fringe.

I drew them myself, and I exaggerated to show what is happening.
I know exactly why this is happening.

I used the lens to magnify a straight line on a piece of paper… I moved the lens across the paper and there were ripples/waves

The lenses at fasttech look fishy… can anyone confirm if they are good?

Nice. Do you specifically need the lens to be 44mm?

I tried this 50mm lens when another member here mentioned that he’d used them some:

I really haven’t used it much, but here’s what I can tell you: the FL is a little long when used in a Maglite. You must either move the heatsink back a good bit more than normal or you must screw the head out until it’s about to fall off. The lens is a little loose, you need to make a ring to snug it up inside the bezel. Someone here suggested just using the edge of a stock lens, but I haven’t gotten around to that yet.

Wow, apparently I don’t have much to say about it. To be honest I put it on an old SSC P7 modded Maglite (P7 looks stupid under an aspheric) just for laughs. I’ve been meaning to do something more productive with one but haven’t gotten around to it.

Come to think of it, I do remember the thread where the 50mm lens I linked was discussed: Aspherical lens adapter for HD2010

Oh youre awesome, thanks for that link to disappointment.

SOLD OUT!!! Shakes head.


I have a feeling that a little scrounging will give you a similar item. It’s just a short tube with a step at the top, similar to a plastic desk grommet. I think you want approximately a 47-48mm ID on the grommet’s tube, then you’d grind/cut down the flange until it fit inside the bezel. (and trim the length until appropriate)

Looks like VOB used plastic tube with an appropriate ID and turned down the OD.

Basically, it has to fit inside a pvc extension. 40mm-47mm