U2 doughnut beam pattern: how normal?

I have a new Surefire U2 s/n A07416 that has a marked doughnut beam pattern (dark spot in middle). From 1 meter and farther it's very noticeable. It's visible on all brightness levels, although slightly more on lower levels.

Does every U2 have this? Or do some not have it? I know some have it and it doesn't bother the owner.

My question is does it always exist, or is there unit-to-unit variation where it sometimes doesn't.

Anybody with a doughnut-free U2, could you please check at the lower brightness levels against a white wall at 3 to 6 meters distance, and post your results? Thanks.

Interestingly on a lux meter the brightness variance in the doughnut is small --say about a 10% variation. Yet to the eye it's very marked, at least on my U2.

Other than the beam aesthetics, it's a great light: very bright, nice handling. Beam color very white.

They all have it, though on many it is almost not noticeable, on others it is very obvious. The tint of the Luxeon plays some part as well.

Some people have sent their heads back to Surefire to fix, and gotten heads with less of a donut, but a tint that wasn't as nice.

From what I can tell, the placement of the LED deeper into the reflector would cure it, but would lose a little focus and throw. As wacko as CPF'ers are about throw, I suspect that Surefire chose to set it up this way.
Bill

Yeah, mine has it. It is more pronounced on the lower levels, but rarely noticeable in real world use outdoors. I did notice it the other night when shining across the street, first time I did outdoors and wasn't looking for it.

As BWaites stated, you could send it back. I didn't with mine because it's not enough of a bother, and I don't want to lose the LuxLotto, since mine is quite white and bright. I chalked it of to there being no such thing as a perfect light, they all have some little thing...

I've read of a few members commenting that theirs really doesn't have a donut, can't remember who or how many, I think it's a low number though.

bwaites said:

...on many it is almost not noticeable, on others it is very obvious...

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Ah, but is that because certain owners aren't as picky, or because it's truly less apparent -- say when viewed side-by-side another U2?

Another complication is distance. At < 1 meter it's much less obvious (at least on mine).

I'm tempted to keep my U2, doughnut or not. It's just incredibly bright -- bouncing off the ceiling or wall of a dark room, my lux meter records about TWICE the output of my HDS U60 on max. Rough as that test is, it seems to indicate the original U2 spec of 100 lumens was correct.

I think someone in the U2 passaround thread purchased one and had the passaround light, and commented on a difference head to head. I read so much on flashlights here it just kinda blurs sometimes. Mine is not a head to head comparision, I'm betting many are not and some are.

I was the one in the passaround thread, and there is a difference head to head.


Bill

It is a general problem of all LuxV lights with the LED in focus.
The cure, as already stated, is moving the LED out the focal point of the reflector, but this will reduce throw and make a bigger hotspot, and apparently this is not wanted.
bernie

My new one has no donut, but what I would say is a very slight blue-ish center. This area, albeit slight, is less pronounced at lower levers. Its plenty white, and really points out how green my L4 is.

best regards

joema said:

Ah, but is that because certain owners aren't as picky, or because it's truly less apparent -- say when viewed side-by-side another U2?

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I think that there are small differences in the size of the hole in the 5W Lux's from light to light.

I have read alot here and witnessed this firsthand also in the L4 lights and KL4 heads. Hole size and tint tend to vary.

I got a KL4 Head from Marty Wiener here in the B/S/T. I guess I won the lottery. It has a beautiful bright white tint and the hole is barely noticible on full power. With reduced power, out of regulation on a TW4 the hole is a little more noticible but still not bad.

Another Soldier got an L4 and his light has a noticibly larger hole than mine.
His tint was still good though and he likes his light.

powernoodle said:

My new one has no donut, but what I would say is a very slight blue-ish center. This area, albeit slight, is less pronounced at lower levers. Its plenty white, and really points out how green my L4 is.

best regards

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This is exactly my u2/l4 scenario! I had the donut (very noticeable) in my first u2 so I sent it back and am very happy with the replacement. (Even with the slight blueish center) I would not hesitate to call for a rma # and send it back. This light costs too much $$ to not be completely happy with it. I sent my original l4 back to the retailer I purchased it from and the replacement came back with the same light grn tint. I won't send it back again. It's not too bad and only noticeable when compared to my u2. I don't want to be too much of a pain in the a@@!!

Fortunately for me, my U2 exhibits no donut, no artifacts in its beam.

I've had 7 U2's, the amount of donut hole varies between all of them(as does the tint). The hole goes from terrible to barely noticable. If its a really bad one I recommend you get it replaced - unless you really like the tint, then sending it back is much more of a gamble. You could get one with a terrible tint and bad donut hole.

I've asked SF and going to send mine back to them because of the doghnut hole. I don't think that there will be any Lux V from SF with a tint as warm as mine. First time turn it on, not comparing to any other Luxeon and I can say its yellow, yellow, yellow.

My U2 doesn't have a donut and has a very white, bright beam. It didn't come this way from the factory. I was able to open the bezel at the junction closest to the LED. I then inserted an O-ring to serve as a shim so that the LED rests a little deeper in relation to the reflector. To correct the greenish beam, I harvested the Lux V from a KL4 I had just bought and transplanted it into the U2. I'm a happy camper. Instead of sending a disappointing U2 back to Surefire, try modding it yourself first, non-destructively, of course. The results may just be to your satisfaction.

Mine also has a donut but I don't notice it outdoors where I mostly use it.
Although indoors it is noticable I am not really fussed about it.

My light has a bright white tint and like torchman mentioned no light is perfect.

I have one in mine and it is noticable but not terrible on lower levels and kinda washes itself out at higher/highest level. The color is on the slightly pink side but isn't bad, its white, no cat urine green in mine.

The hole is barely noticable outside, have to really look for it.

grnamin said:

...open the bezel at the junction closest to the LED. I then inserted an O-ring to serve as a shim so that the LED rests a little deeper in relation to the reflector...

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Could you give some more details? What material, size, and thickness of O-ring? Where exactly (relative to the emitter) and how did you insert it?

joema said:

Could you give some more details? What material, size, and thickness of O-ring? Where exactly (relative to the emitter) and how did you insert it?

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I think it was a 3mm O-ring, neoprene, don't know what size. It should be smaller than the diameter of the threaded section of the bezel at the LED level. Got it from Home Depot. Please note that some U2s can't be opened because of the thread weld. Mine had very little so I was able to open it up by hand on the first try. I first removed the reflector section, slipped the O-ring over that section, screwed it back into place but left a gap just wide enough to roll the O-ring into it. I then tightened the assembly hand tight so that the O-ring would seal the gap and serve as a shim. Hope that helps.

Here's a post showing the opened section of the U2:
http://candlepowerforums.com/vb/showthread.php?t=68819. You can see the O-ring shim in the second picture.

I got lucky on mine... It is very white...like a HID white, with not very much blue at all...just nice crisp off white...with a tiny bit of a shadow spot in the center that you have to actually look for to see. :- ) on the wall it's noticeable, but outside you have to move your eyes around a little and look for it to actually see it.

socom45 said:

...tiny bit of a shadow spot in the center that you have to actually look for to see. :- )...

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The doughnut pattern is so clear on mine it looks like a smoke ring. It almost looks like the M57 astronomical nebula, minus the color: http://www.seds.org/messier/m/m057.html

I called Surefire, they were very responsive, said it's not normal send it back and they'll fix it.