tight spot/diffused spill

A good beam to me for outdoor use might be one with a hotspot (maybe a larger spot like a XP-G) but with a diffused edge to the spill rather than an abrupt edge as it goes from spill to complete darkness (the XP-G already seems to have a smoother transition from hotspot to spill than the XR-E).

Simply using a reflector you get that abrupt drop-off along the outer edge of the spill. Using an optic like an aspheric you have no spill and simply the hotspot and then the drop-off.

In a TIR optic there is usually a little collimation lens on top of the emitter to capture some of the direct rays that otherwise would contribute to spill and to focus it to contribute to the hot spot which also reduces spill a bit.

Instead of a collimation lens what if a small diffuser was used. This would either just be a replacement for the collimation lens in a TIR or it could be a small diffuser over that same part of the emitter even if a reflector was used instead of a TIR.

The spill comes from those direct beams that don't hit the TIR or reflector. If that was diffused it wouldn't affect the hot spot. Therefore it would seem that you would have a hot spot with a diffused spill and there would be no sharp drop-off at the outer edges of the spill beam. It would be like a flood beam where you aren't really aware of exactly where the light stops.

Am I missing something? Would this not work? It would seem to be a much nicer beam and still provide throw.

It's always distracting to have your eye trying to focus on whatever the hot spot is illuminating when in your periphery you see this huge circle of spill shaking around. Without that hard outer edge you wouldn't see that movement just as you don't notice movement in that outer edge when you use a flood beam.

On one light that I had built for myself I noticed that the little collimating lens over the emitter resulted in a square corona around the hotspot, much like you would get from an aspheric lens. I dusted the collimating lens with some window frosting spray and the square corona is now gone and the result is a nice beam that looks like you used a McGizmo OP reflector, albeit with a lot less spill.

I've experimented with using the frosting spray on only the outside edge of the lens on reflectored lights with some decent results. I was trying to smooth out the horrid beam from a SSC P7 Mag build while trying to retain some semblance of throw. I've since given that lens away, but, I might revisit it and see what it does on a single-die light.

Okay, some beam shots.

First light is a dual setup. Note the square corona:


Second shot is a single setup with a different emitter than the first one, but, it's the same optic:


Sorry, the second shot was much dimmer than the first one because the first light was direct-driven and a dual setup while the second one is driven at 250mA. You get the idea, though: the square corona is gone.

PCC said:

On one light that I had built for myself I noticed that the little collimating lens over the emitter resulted in a square corona around the hotspot, much like you would get from an aspheric lens. I dusted the collimating lens with some window frosting spray and the square corona is now gone and the result is a nice beam that looks like you used a McGizmo OP reflector, albeit with a lot less spill.

Click to expand...

Thanks for the pics.

I've experimented with using the frosting spray on only the outside edge of the lens on reflectored lights with some decent results. I was trying to smooth out the horrid beam from a SSC P7 Mag build while trying to retain some semblance of throw. I've since given that lens away, but, I might revisit it and see what it does on a single-die light.

Click to expand...

I'm trying to picture how this would work. The hotspot (when using a reflector) comes from the outer edges of the reflector (simplified) and eventually are focused to form that hotspot. I would have thought that spot (focal length) would be outside of the flashlight and therefore frosting the outer glass lens (edges) would simply break up that hotspot. The spill comes from the direct rays of the emitter (those not hitting the reflector). I could see somehow frosting the very top of the led.

I've done what you are talking about (except I was using translucent tape) with aspherics which operate on a different principle but with a reflector my experience was that it doesn't work. I was doing it with an aspheric just to clean up some artifacts outside of the spot.