Fenix TK35, Donut Beam

[Onebadengine]

I work in an underground mine as a mine foreman and part of my job is going around to every section of the mine that someone will be working at and doing a pre-shift inspection.(checking for loose ground) This is a underground stone mine with heading 27' high x 48' wide, a little bit different then coal. We have regular mining cap lights but honestly they are way behind times with there incandescent design and even the led version are nothing to brag about at 130 lumen's and around 4-5k lux. That's why I recently purchased a new TK35 because of the compact size of the two 18650 layout, run-times and total amount of light it produces. the light is a little bit big for an edc for the average person, but to me its not that bad at all with the layout of the tk35. The light that it puts out makes my mining light look like a candle burning. I like everything about the Fenix besides the quality of the beam, it has a big dark spot right in the middle of the hot spot with a greenish tint. When the light first came I was excited that it arrived and quickly popped in some cells and tried it out. I was disappointed with the tint and the big black hole in the middle, I knew that I would not be using the light indoors and thought that it would be alright. After using the light for about 2 months underground and outside in the dark it became unacceptable. After looking at some beam-shots of this light on the net, I decided it would be like playing the lottery. I like everything about this light besides the quality of the beam, so I took the plunge and ordered another. Well needless to say, the other one has just as bad of a donut hole and a greener tint to it.(That's why I don't play the lottery) It has been almost 6 months of using the first light and every time i turn it on the big dark spot bugs me worse and worse.

I have other lights but none as compact with the run-times and shear output of the tk35. I come to this site on a regular basis hoping to find my new light but nothing excites me. I need a light that throws pretty good but not one without any spill. I think that if the donut hole was fixed on the tk35 it would be a beam without compromises, good throw and spill.

Why do some of them have a good beam and others don't? Would replacing the led with another fix the donut affect? Can this be done?

The led on both of my lights are not perfectly centered, would this be the cause?

Any information on how to fix the donut hole would be greatly appreciated, and sorry for so many questions
Thanks, Gary

 

[roadkill1109]

After reading your post, I took out my TK35 and examined the beam, the only time the donut hole becomes apparent with mine is when you are illuminating something a few inches away from the light. How far away were you testing the beam for donuts? Because all of these lights, (even my Quark) when you illuminate something near enough to the light, a big donut appears in the middle. I'm sure its the limitation of the reflectors in each of these lights.

And the tint lottery, I guess most of the XML's the TK35 come out in have a greenish tint. It only becomes quite noticable running them at the lower modes. High and Turbo, its almost white. What modes do you run your TK35 on?

Anyways, if you prefer a whiter beam, you could look to the R5's. There might be some whiter XML's but im not sure which bin is the whiter ones, maybe the T6(V20C), or the U2(TK21), not sure, i dont own any of those. (yet)

But bottom line, build quality and durability, you'd never go wrong with a Fenix!

 

[Onebadengine]

The donut hole in mine is apparent from 15-20 feet and gets worse the farther away the object is. I mainly use my light on high and if that is not enough I'll bump it up on the turbo mode. The only time I use the lower modes is if I am looking for something in my truck or something close up. I wish mine only had the donut a few inches from the beam. I sometimes shine it out across the field wondering where the horses are at, and at roughly 50-60 yards the dark spot in the middle on both of my lights are a little bit smaller than one of the horses. They are saddlebreds that range in height from 16 to 16.7 hands tall, not a small horse.

Wanna trade? haha, just kidding.... I'll get something figured out. How well is your led centered in the reflector? Neither one of mine is centered very good, wonder if that is the problem.

I could live with the greenish tint but the black hole is really annoying and bugs me more and more with use

 

[roadkill1109]

Trade? Naaah! Hahah If you dont mind my asking, where did you order your lights? And if the donut hole is that bad far out, you should have it replaced. Mine's perfectly centered, i'll post some shots later when i get to the office. You know, that off-center led might be the problem. But it is strange that Fenix still has that problem with their TK35s, i know they got it sorted out already which is why i purchased mine later this year. Could it be an old stock?

 

[roadkill1109]

Here's my TK35!

Here's the shot of the LED, please bear with me, i just used my Blackberry to take the shot:

then here's the beam shot showing the donut up close:

i just love this light! green tint and all! (hehe)

i didnt notice any donuts here. (low beam)

here neither (high beam)

i'll try taking a futher out shot come nightfall

 

[Stress_Test]

Jeez, it's hard to believe that any established manufacturer would still have problems like this with unfocused beams, but apparently they do!

You might try some light texture diffusing film on the lens to smooth out the beam. It will reduce the throw, however. I don't know offhand what's popular right now for diffusing material, but a cpf search should turn up some threads (I think this was done on the earlier TK40 and TK30 also).

If you're feeling more adventurous I suppose you could try opening up the head and adjusting the position of the emitter to find the sweet spot. If there's still a chance of getting a warranty replacement I wouldn't do that though. ('course, I'm a ham-fisted gorilla when it comes to delicate electronics work, so I wouldn't try it myself anyway!)

 

[Buckley]

The beam my TK35 emits is flawless. I would recommend you send yours back from whence it came for replacement.

 

[veedo]

i have 2 tk35's. one has a perfect white beam, the other has a green donut hole beam. the green donut hole one has the warning label on the head that ends up off to the side of the light like in the picture above. the perfect beam tk's warning label on the head lines up with the side of the body. there may have been some earlier versions that werent perfect?

 

[Rees]

I just got my tk35 in a few days ago and had to send it back because it was tinted green and pretty bad doughnut. there was a small bright spot in the middle then a fairly dark spot then it was green outside of that reguardless of how far you shine the beam. kinda disappointing, ive been wanting this light for awhile. we will see when i get the replacement.

 

[MDJAK]

I got mine about a week ago and beam is perfect.

 

[00ChevyScott]

While mine does have a green tint to it, mine does not have a donut problem

 

[NickBose]

Mine does have donut beam

 

[bl4ck4dd3r]

With my TK35 arriving only yesterday I was curious to see how it's beam compared to those of the OP.
Being red / green colourblind I was not concerned at all about any tint and typically use my 'light way out in the countryside
where there is no other light than that of the moon and stars so whatever light i can get is more important than the colour temperature.
What I was most looking at was whether my 'light would exhibit any doughnut effect or black spot.
My experience is that I can only create a black spot at under 3 inches and then only on the lower three settings, anything over that and
irrespective of the distance and setting there is no black spot.
With the doughnut , again I can only recreate this at short distances at around 2 feet or less and not at all on Turbo.

Being completely new to all this my thoughts are probably naive but isn't this likely a problem of the position of the LED within the reflector ?
wouldn't even slight misalignment contribute to these kind of artifacts ?

 

[Rokron]

I've got one about 3 months ago and mine has a perfect bright white beam, up close, far away and in between. It was my first serious LED flashlight.

 

[Rees]

Just put in order today for new one to replace the green doughnut one, we will see if i got a good one this time tomorrow.

 

[Spypro]

I bought a TK35 last summer and it has a slightly perceivable donut hole. It is not a problem when I use it. Here is a picture of it (exposure stepped down).

 

[Cataract]

I don't have a TK35, but I have almost 30 Fenix flashlights and all the beams are pretty much perfect.

There was major concern about a year ago that there where some cheap Fenix clones being sold from China... maybe this is the case? Who's your dealer?

 

[Spypro]

I bought mine on fenixtactical.

 

[BLUE LED]

I am tempted by the TK35, but I fear the dreaded green tint on turbo and black hole :O

 

[Cataract]

I bought mine on fenixtactical.

Your slight donut hole is normal for lights of that size range, since the reflector is what makes the throw, not the LED. My LD40 has the same profile among quite a few other lights. I don't believe you would get a cheapo replica from Fenix Tactical (all my lights come from there and I've been in touch with Alex often.)

What worries me are the ones with an actual donut hole that is visible and bothering people at 15-20 feet in real life uses.

[...]
Being completely new to all this my thoughts are probably naive but isn't this likely a problem of the position of the LED within the reflector ?
wouldn't even slight misalignment contribute to these kind of artifacts ?

Seeing a donut hole at 3 inches is normal. Any flashlight will exhibit that hole if you hold it close enough (I think someone already mentioned this but I didn't feel like reading the whole thread again.) Uncentered LEDs will definitely lead to weird beam profiles as well as possible very dark spot centers. Just open up an old flashlight and play with the reflector position and you'll see some ugly beams.