XP-L HI V3, Aspheric design, LED surface brightness...

I have an XP-L Hi incoming. Do the factory de-domed emitters spread more light sideways than their domed counterparts? What is the effect of the LED dome?

I ask because I have an aspheric DIY project and I am wondering am I going to lose more stray emitter lumens (radiating sideways) with a de-domed LED?



For this project I want to try a DIY Waiven collar. poor-mans deft-x if you will. Reflect all the sideways-spherically radiating lumens (stray light) back down onto the LED die to increase surface brightness. As opposed to using black paint / marker to absorb stray light inside the bezel.

I think I can use one of these hemisphere molds, drill out a hole in the center and polish it to a sphere mirror.


All else equal, de-domed emitters (including the XP-L HI) emit less light sideways than their domed counterparts. That’s the whole draw of them… a more narrowly focused beam.

OK great thanks!! added some more commentary to my OP.

Subcribed , keep us updated with the project here :beer:

Please search for the explanation from Dr. Jones regarding dedoming. It has nothing to do with the angle of the emitted light.

Also it is not advisable to use a stainless steel collar because stainless steel doesn’t reflect a lot of blue light. Blue light makes the phosphor of the LED more intense.with a stainless steel collar you will probably only get around 30 percent more intensity. A real collar can increase intensity by up to 120 percent.

An aluminium collar would be much better. Polishing it yourself will be difficult. A real mirror is better.

Prepare for a science lesson! I’m still working on digesting it:


OK thanks gents !!… Some great info there.

I never even thought about the reflective properties of one metal versus another.

The HI version is not dedomed.
It just has a flat plastic surface rather than a domed one.
You can look at the emission graphs, the HI version has higher intensity near 0 degrees and less intensity to wider angles.

I am just trying to find something better to do with all that stray light, than to have it soaked up in black paint or sharpie marker ink.

Oh ok then… so is it more like a razor sliced dome? I did manage to find those emission graphs after posting, OOps. thanks


Yes, but that doesn’t seem to change all too much and the effect is the same. The HIs are good if one wants more reliability and ease of handling.

A de-domed XP-L V6 oder W2 will be better.

I am still a bit wondering why its not possible to produce V5 or V6 XPL-HIs

I think its because of the “missing” dome which would typically give any stray photons a chance to reflect back against the phosphor layer and product useable light. That’s probably not quite the right terminology… but you get the idea.

Same principle on traditionally dedomed LEDs - you gain throw at the expense of some lumen output.

You can see from those graphs that the HI is better for aspherics.
Also remember that they are individual percentage graphs, so the 100% peak for the HI is actually more intense than the peak for the non-HI, even though they both show 100% in the center.

I tried this:

Just to see howe it went....the reflector is taken from a BLF A6, and it fitted just perfect down over the LED on the UF-1405.
But it was not a positive test, in my eyes....

That’s because you used a parabolic reflector not a spherical one, and also because the opening is waaaay too small.

A parabolic reflector won’t work. The reflector needs to be a sphere… technically its a hemisphere or half-sphere. The emitter should be placed at the focal length of the sphere, or in this case the exact geometric center of the hemisphere. The hole needs to be big enough so that it allows light a straight path from the die to hit 100% of aspheric glass. An opening too small will block light, as MortyDuck discovered. An opening thats too big will waste stray lumens on the bezel/host. I would imagine its better for the opening to be slightly too big than too small.