High Grade XM-L Optic, Need Suggestions

Hi Guys…I am looking for an optic for an XM-L project that needs excellent beam uniformity, preferably sharp beam edges and a reasonable efficiency, above 85%.

I was considering the $1.50 ones at Illumination Supply, where I’ve bought parts before, but would like to pay more for a higher grade material such as glass/quartz/etc., an AR coating or anything else that enhances performance.

FYI I work with reflectors and want to try optics for a more compact flashlight and to transfer the spill to the beam—optics do these things, right? Also any tips for an experienced builder but new with optics would be appreciated.

Thank you and I appreciate your feedback. :bigsmile:

You will never find 85% efficient optics. You are lucky to find 70% efficient.

I suppose there are different ways to define and calculate the efficiency…

I’d like it to be reasonable, but I’m primarily concerned with how the beam pattern and spill (if any) look.

you’ll struggle to find an optic that has a sharp cut off to the edge of the beam/ spill, certainly nothing like a reflector. The closest I’ve ever seen to that is with a Ledil LC1 (no holder) or Carclo 26.5mm (or was it 28.6?) tight spot optic.

Most of the spec sheets for Ledil and Carclo spot optics specify ~85% efficiency, although wide angle or diffuse optics are generally less efficient. I don’t have the skill or knowledge to call that value into question, so I just have to take it at face value.

Thanks for the info.

FYI while searching these I found the beamshot thread. The flood optics definitely are better than reflectors for mountain biking. Spreading the light evenly over 30 to 40 degrees is ideal but difficult to accomplish.

But for flashlights I don’t quite understand the appeal of optics since it reduces both the throw and the total lumens.

The “out the front” lumen reading divided by the bare emitter lumen reading…

Just an uncoated lens on the front of the flashlight drops the light level around 10. A decent coated lens around 2. Reflectors and TIR optics can easily eat over 20% of the light coming from the emitter. Add to those losses things like light being absorbed by the flashlight bezel, etc and never expect to get more than 70% of the light coming out of the emitter onto your target.

no worries :slight_smile: I think it’s just a preference thing. I don’t need to see huge distances (my children have their own torches and are easy to find), but I like a smooth transition from spot to spill, so optics are more pleasing to me. Plus I use my torches a lot for close in work around the house or when camping, so a very bright spot with a dim(mer) spill is counterproductive for me. However others use lights more for distance work, so large reflectors or aspherics make more sense.

I’d agree with the “OTF lumens = 70% of theoretical lumens”, but as you said that’s made up of a bunch of different losses, including heat sag, so it’s easy to misread your original post as ascribing all of that 30% loss to the optic. I’m guessing that what you’re referring to as “optics” is the whole shebang between LED and the outside world, whereas agatator07 was talking just about the chunk of plastic sitting on top of the LED :slight_smile:

Nope, those are just optical losses… lens, reflector, bezel, anything between the emitter surface and the outside world. Heat sag not included…