Convoy C8 focusing

I’ve heard from several members that you need to sand the bottom of the centering gasket to achieve perfect focus in the C8. Some say up to 0.5 mm, but this doesn’t make any sense to me. The stock gasket is almost always 2.07 mm and I’ve tried sanding 0.1 mm at a time to see if it gets any better. But it never does? The wierd thing is that the hotspot gets smaller and more defined when sanding, but when testing it with a lux meter it gets worse.

I’ve tried one gasket that I’ve sanded down to 1.7mm in 7 different C8s and every time it gets roughly 15kcd worse than stock.

Anyone who can chime in?

At what distance are you measuring?

5 meters.

You may want to try a little further away - I usually do throwers at 10m.

But the thing is, you will just be adjusting the focus to a single point; 5m, 10m, whatever you are taking the measurement at. The beam will be ‘out of focus’ before & after that particular distance.

Here’s an interesting post by Enderman regarding focusing.

The convoy Reflectors work great with XML2, with dedomed or XPL HI the throw gets better, but not near other expensive lights

Klarus XT12GT XHP35 and Convoy with XPL HI both had for me the same spot diameter, even if the C8 had a smaller die

I’ll try measuring further away, but I think I’ll be getting the same results.

Mitko is one of who told me about 0.5 mm. And he gets way better numbers than me at even less distance. I’ve tried measuring at the same distance as he does with a sanded gasket and I still get worse results than with the stock gasket.

It sounds like you are going through the right process. Have you tried increasing the thickness?

It could just be a combination of the parts you have - maybe the centering ring is already very thin?

What LED/s are you using? A domed LED will have a different sweet-spot to a de-domed for instance.

Smaller dies require the centering to be very accurate as well.

I haven’t tried that, but I have a few gaskets that it can try it with. Problem might be that the bezel won’t screw all the way down then.

I don’t think so. I use the same as Mitko and Richard over at MTN.

I mostly use XP-L Hi.

I guess the other question is what current you are driving the LED at, & the bin of the LED.

Hope you get it sorted out - playing around is half the fun :+1:

6 amps and V3 3C.

Thanks, I really hope so too.

I don’t know if I agree with you there. I’m getting pretty sick of all this measuring :stuck_out_tongue:

Hmm, this makes me think I may have made mine throw less then, The theory I used was this, If I hold most all of the other lights I have on a very low mode close to a wall , I see a very faint cross in the hot spot.

I have been told this is the reverse image of the square LED.

The Convoy C8 XPL HI I have showed a hole in the hot spot on this test , so I moved reflector closer to LED (thined centering ring) and got same faint cross as others.

This seamed to give a more intense hot spot a shorter distances (5 to 10 meters).

Have I actually reduced the maximum throw at its farthest point? Say 400 meters?

This is also what I want to know. If I understand Endermans topic correctly, it would seem that you shouldn’t try to get maximum candela at short distances. What I mean is that less candela at 5 meters could actually be more at much longer distances?

But this should also mean that every manufacturer and pretty much all modders here are chasing the wrong number?

if the hotspot is more clear for your eye the throw should increase
it is true that a defocused light can show at 5m more throw than one focused to infinite

I think it was mainly me who claimed that a thinner LED gasket will focus an XP-L HI better in a Convoy C8.
But this was my conclusion at the time.
I was a little disappointed in the tightness of the beam when i got my black C8 with XP-L HI U6 3A.
It did improve when i sanded down the bottom of gasket.
But i needed a thicker O-ring in the bezel too.
…but i discovered later that was also due to the thinner AR coated lens i put in… :person_facepalming:
(I also sanded down the top of the gasket by the way, because it was shrouding the LED a little.)

Is there a way to tell if the gasket is shrouding the LED? Also, do you remember how much you sanded the bottom and top?

Mine is 0.5mm thick between reflector and LED board, total thickness of the gasket is 1.2mm (1.5mm would have been fine too.)

You can look if you can see the LED die reflect from the narrowest part of the reflector.
Basically, when you see white there, the gasket is in the way.

It doesn’t matter too much though, at those angles not much light is emitted by the LED and it ends up as ‘corona’ anyway.

Only 0.5mm? Doesn’t the reflector lip touch the body before that?

Did you test with a lux meter or just by eye?

Yes, the reflector lip / rim touches the body on mine, but only just.
Let’s say the reflector pushes down harder on the gasket than on the body.

I tested by eye.

I can now confirm that lux numbers really don’t say it all. A light with 125kcd throws less than a light with a smaller spot and 110kcd.

Took the lights out to compare and the one with much less candela clearly throws further.

That’s weird.

So, how much space do you have now, between reflector and LED board?