Extra ring on outer edge of beam? Terminology? Cause?

Off-topic Chatter
1

I have noticed that some lights have an extra, dimmer ring of light around the outer edge of the beam. I’m talking about single emitter lights with round reflectors. What causes this extra ring? Does it have a name? How is it prevented via design or remedied via modification?

An example of this would be the Catapult V6. (Though that one doesn’t bother me so much because it is a thrower anyway.)

2

There’s no special term for the ring.

In most cases it is caused by a design issue. It can be caused by:

  • The design of the reflector - sometimes swapping in a different reflector solves the problem. A good example is the 2012 version Jetbeam RRT-01. The original reflector was tremendously ringy. Swap in a different reflector and the beam became perfect with no rings.
  • The type of reflector - Orange peel reflectors tend to be more forgiving than smooth reflectors as the orange peel can sometimes smooth away small rings. However, it should be noted that even smooth reflectors can be made with no rings in the beam.
  • Whether the reflector is optimized for the LED - it is important to pick a reflector that is optimized for the LED and is the right height above the LED. Rings might develop if the optimization is not quite perfect. I experienced this when modding an Emisar D1… the default beam with XPL HI and smooth reflector was perfect. But when I swapped in a sliced SST-40 the beam did gain a few minor rings.
  • The housing - For example, some lights gain a ring in their beam from reflections off the inside of the steel bezel. If that’s the case you can reduce the ring by covering the inside of the bezel with something to reduce reflections. Even a black sharpie might help.
  • The led - I recall some early lights gaining rings from the design of the lens. I recall this in some old CREE XRE lights as that LED had a glass lens mounted on a metal ring. Light would reflect off the metal mounting for the lens and create a ring in the beam. This should not be an issue for modern LEDs that use a silicone lens.
3

My Zebralight sc700d has the “ghost ring” while my SC64c LE does not. Both have OP reflectors. I guess that the sc700d bezel could be partially to blame, or maybe the reflector is not optimized for the led. Zebralights are hard to modify so I probably won’t try anything with that light, but I wanted to know more about this phenomenon so that I can avoid it. I’ve seen people describe lights as having “no artifacts” in the beam but this right was present.

4

I do not get the outer edge ring every six months. For me, it happens annularly.

5

On a couple of my Convoys it was the SS bezel causing the rings.

6

This.

Most common cause is the bezel. Unless it’s very matte, it’ll create some reflection. Polished or as machined SS are the worst. Even ths black Ti coated bezel on an Eagtac causes some periphery artifacts. I’ve seen certain AR coatings cause a colored ring at near 180° to the lens, too.

7

:laughing: i was thinking that you had some sort of annularity issue, hope it gets better for ya.

Did you ever wonder if Latin flashlight beams displayed an annulus?

An annulus is the region between two concentric circles. Informally, it is shaped like a ring or a hardware washer. The word “annulus” is borrowed from the Latin word anulus or annulus meaning ‘little ring’.

8

This makes sense to me but for whatever reason the smaller light doesn’t seem to suffer from this issue despite having an almost identical design. Also the TN42 has it: TN42 - ThruNite Official Store Truly this is nitpicking though because all of these lights are really solid performers.