I want a U2 - but I'm worried about the "donut hole"....

I would like to get a U2 (probably from OpticsHq) but I'm very apprehensive about getting one with the donut hole. If I should get one with the hole, is there a way to repair it? Or would it be better to send it back to Surefire? I thought I read somewhere that Surefire would not repair donut holes anymore. Is that the case?

The U2's bezel can be difficult or impossible to loosen and open without damaging the finish. If you're able to loosen the bezel, you can shim the LED in relation to the reflector by added another O-ring into the bezel gap. The shim will reduce or, better yet, eliminate the donut. With the bezel open, you can also replace the emitter, if not to your liking, with a better one.

Hmmm. I may just go with KL3/G2 combo with a McE2S 45 or 60 ohm 2 stage switch in the tailcap....

Why is it such a concern if you get a donut hole?

Will you be doing alot of wall hunting?
I own 2 Surefire U2's and they both have a slight donut hole, but they are very bright and I don't even notice the donut holes when I am actually using them in the real world. The donut hole is so over rated... just remember it is the design of the 5w LED's and not the flashlight.
I think you will actually like the Surefire U2 once you use it in person, and not judge it from heresay. I know I was blown away by it's performance once I used mine in person...plus I bought my 2nd U2 after I saw for myself how good this light really is in performance and quality!!!!!!

The donut hole bothers me terribly. I bought an L5 a while back that had one and sent it back, luckily they sent me one that is perfect.

Well... it's probably not the donut hole itself persay that would bother me. But the fact that i'm spending that kind of money on a flashlight.Not only that, a "perfect beam" guarantee is in writing from surefire. So it's not really about the donut itself, for me it would be the principle of the thing.

KDOG3 said:

I thought I read somewhere that Surefire would not repair donut holes anymore. Is that the case?

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I hope to God this is true.

I've met two people who actually use the U2 for their job and although I noticed both lights had a donut hole neither person said anything about it at all. Unless you have built up a hatred of the donut hole and as such have an increased awareness prior to owning the light you just aren't going to notice it.

For you, I recommend you just stay away from 5 Watt lights that use a reflector.

The donut hole bothers me terribly.

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Why? What are you using your lights for that it is such a problem?

Why in the world would you say something like that? Why start a flame-fest? Surefire HAS to know by now that people don't like the donut hole. So why make them?

Also, I was just asking. The beligerant tone was unneccessary.

KDOG3 said:

Why in the world would you say something like that? Why start a flame-fest? Surefire HAS to know by now that people don't like the donut hole. So why make them?

Also, I was just asking. The beligerant tone was unneccessary.

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Please understand, no belligerent tone meant at all. I was making a point that the donut hole is actually preferable to me because it noticeably improves the beam characteristics during use. Please don't start a fuss because you disagree or dislike my opinion.

Also, apparently most of the people I have spoken to or read information from who use their 5 Watt Surefire lights (LEO, Military, Cavers + Explorers) don't have any problem with the donut hole, it just does not register with them. Perhaps this is due to the fact that many are issued their lights and are not forking over 300$ for a flashlight but this complaint of the donut hole really only seems to be limited to "collectors."

I was honestly curious as to what use you put your lights to that the donut hole bothers you. I use a 5 Watt light with a donut hole and haven't encountered a circumstance in which the donut hole was a problem.

And that was a serious recommendation about the 5 Watt lights with reflectors, nothing is worse than trying to play donut-hole-lottery for a 300$ U2 and losing.

My suggestion for you guys that have problems with donut holes and Surefire is that you buy from a different manufacturer that is far superior, and has no problems at a very cheap price. I don't think anybody is forcing you to buy/look at Surefire...it's a personal choice, and I chose to pay for the 2 Surefire U2's that I truely appreciate owning. (I don't have a bunch of money to throw away on junk...that's why I own Surefire).

Alin10123 said:

Well... it's probably not the donut hole itself persay that would bother me. But the fact that i'm spending that kind of money on a flashlight.Not only that, a "perfect beam" guarantee is in writing from surefire. So it's not really about the donut itself, for me it would be the principle of the thing.

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grnamin said:

The U2's bezel can be difficult or impossible to loosen and open without damaging the finish. If you're able to loosen the bezel, you can shim the LED in relation to the reflector by added another O-ring into the bezel gap. The shim will reduce or, better yet, eliminate the donut.

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You lose a good bit of output when you do this (as spoken by my light meter)

I'm also concerned that the lack of m2m contact between the reflector and can will not allow for effective heatsinking.


KDOG3,

So far the best solutions I've found for the donut hole:
1) stay away from CPF
2) don't have tan walls in the house
3) ..seriously.. some emitter tints will cause you to notice this _correct_ attribute of a 4 die emitter. So far I find it more noticable with a greener tint than a white/blue


Remember this is not a U2 specific problem. The L2,L4,L5 all have it too...that is how they are designed. Focusing it out of a traditional reflector will compromise throw. I suggest anyone worried about a donut hole get something else because they will only obsess about it and not enjoy the light.

I think two things fuel the donut controversy:
1) Surefire guarantees a perfect beam (as KDOG3 stated above).
2) Others have reported getting U2s with donut-less beams right out of the box.

Hmmm... Maybe Surefire should come up with a U2 that uses an optic instead of a reflector or a head with a deeper reflector or equip the U2 with a K2...

Totally agreed that the donut hole problem is overexagerrated around here. I have a U2 also that has a slight donut and it has bothered me none in real world applications. I own 2 other Lux V's, the L5 has a slight one and the L6 none at all, and quite frankly I would use any of the three in any situation ( except one that called for longer runtime then id take the L6).

Somone once said here that because the Lux V's donut hole as a manufacturing characteristic that if your light is actually showing the donut hole it means your led is perfectly centered in the reflector. Have no idea if this is true or not but could make sense.

It sounds to me like a donut hole *IS* technically a perfect beam, just not the kind most are used to, since a properly focused LuxV in a reflector makes a donut. But maybe I don't know squat.

my dad has a donut hole in his U2 and I didn't notice it until now because of this,they've never been an issue,it's not that big of a problem,I don't blame surefire If they stopped fixing these because it's not something that demands so much attention there are better thing for them to worry about than a donut hole.When your donut hole starts to look like a beam of a 2 dollar rayovac then you really complain.

nc987 said:

Totally agreed that the donut hole problem is overexagerrated around here.

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Depends. Some donut holes are far worse than others. Some are hardly noticeable. And others are faw worse. It all really depends if youre lucky or not.

I think the best way to get a U2 is go to a local store and see the U2 out of the box.

grnamin said:

I think two things fuel the donut controversy:
1) Surefire guarantees a perfect beam (as KDOG3 stated above).
2) Others have reported getting U2s with donut-less beams right out of the box.

Hmmm... Maybe Surefire should come up with a U2 that uses an optic instead of a reflector or a head with a deeper reflector or equip the U2 with a K2...

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1) I don't think they do anymore :nana: http://www.surefire.com/maxexp/main/co_disp/displ/carfnbr/0/prrfnbr/24187


"Our flashlights produce optimal beams — no dark holes, rings, hot spots, or shadows"

(seriously what is a perfect beam?? A 200lux deviation in the center is all we are talking about. The comparison has always be vs a Mag ---well we really know that is the case--- so yes it is a perfect beam. I think we have to agree a the LuxV produces a radially perfect beam without the batwings. If I were to describe a perfect *perfect* beam, the hotspot would encompass the illuminated area with no deviation in intensity. )


2) I believe that the people that have a donut free beam from the factory fall into 1 of three categories.

-a) use the light for its intended purpose --ie no wall inspections
-b) have a tint that makes the observation of the max 200ish lux center of beam difference less of an issue. For instance, the donut hole on my U2 was much more noticable before the emitter swamp. The greener stock emiter showed on white and really showed on my tan walls. The hole with the WWOS can be witnessed on white __if you really look for it hard__. On the tan walls it is a little easier to see. Neither was noticable without being very anal in the inspection and both are great performers
-c) have a unit that doenst show a distinct donut due to improper focus at the factory. If I were to guess they are also the ones that would only register 1600-1800lux whereas the properly focused lights max around 2200-2400lux (my light is higher than that with the WW0S).




I could get rid of the distinct donut hole, even did it once accidentally because the oring was being compressed before seating all the way. When I put it on the meter I quickly decided to figure out how to get the guy to seat properly. If I were to bet, the donut free (without a reflector change) units just didn't get tightened down all the way. My SN is 727 btw, so it is an early unit.

YES, I want to try a W or Xbin TIRed U2


EDIT

I hardly notice the doughnut with mine, except when looking at cream coloured walls.
Outside it never is an issue; I've never not had enough light in the center (darker area) while having enough light just outside the center of the beam.

I have a modded Lux5 light where I can put the Lux in and out of focus. With this I can unfocus the light an loose the doughnut. When doing this I loose throw and if the reflector is raised I loose output as well.
If the reflector is seated further down I don't loose output, but I do loose throw.

I think somebody on this forum said he tested Lux5s on stars and most of them showed a doughnut even without the reflector... The ones that didn't might be the kind to give doughnut-free U2s with good throw?

I don't think there is very much SF can do about the doughnut-issue and since most of their sales come from outside CPF I don't think they are too worried about it....

Sverre

We've been down this road before, so I won't repeat myself... even with all its quirks, I like the U2, and I'll leave it at that.

I will say, however, that even after reading up on it, I am still not convinced that a "perfectly focused" LuxV (maximized for throw, essentially) must carry a donut by default. I am yet to see strong, inequivocal evidence (or a sound optical explanation) for that. At some point I even understood and believed the hand-waving, but not anymore.

greenLED said:

I will say, however, that even after reading up on it, I am still not convinced that a "perfectly focused" LuxV (maximized for throw, essentially) must carry a donut by default. I am yet to see strong, inequivocal evidence (or a sound optical explanation) for that. At some point I even understood and believed the hand-waving, but not anymore.

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A lil butter for that popcorn...


First off we have a reflector with the sole purpose of projecting the image of the whatever is inside it. Diffussion (stimple in this case) is utilized to soften/homogenize the projected image

The very center of the die is a cross(remember it is 3d and is lower than the top of the die). It produced some light due to the presence of phospors at the edges of each sub element on the die but at a lower level.


So would one expect the image of the cross to be present in the center of the beam of a properly focused optic/reflector? I would.

Can you 'tweak out" the image of the null region without degrading throw? I cant see how as long as we are discussing a traditional reflector. You only have two real options to diffuse the image: defocus to blur it out or have a more agresssive finish on the reflector. When you defocus the U2, you not only disturb the colimination of the beam but you drop a portion of the emitter below the reflector thus losing light output. We al know that more stimpling or a diffusion film can clean it up but there is no doubt on its effect on throw