Review of Fenix TK41, with measurements and outdoor beamshots

[Fern]

Red-T - at very close range the dark clover-shaped center is there on mine also. There are various colored rings in the spill/corona as range is increased noticeable on white wall especially but I believe this is just typical of a smooth reflector.

burpee - The reason I was moving the light around was to make it easier to see the donut hole and ring effect. It's just not anywhere near as distinct in the video as it to the naked eye. It is obvious regardless of what object the light is illuminating, that's why I noticed it immediately. I understand what you mean about holding the hot spot steady then moving back and away, I tested this several times with a friend to check if I was imagining it

As I mentioned it was quite difficult to capture the effect on camera. Still shots were impossible because the reflected light was too great even on medium level and the hot spot looked completely full, white and 'normal' regardless of camera settings/setup and target surface.

That's why I switched to video.

I am very concerned this beam pattern is abnormal and will affect throw negatively. I have still not received a response from Fenix regarding this matter.

 

[burpee]

Well I don't know jack-squat about light, physics or flashlights, but I know what "bright" and "throw" mean in torch-speak. And I can tell you right now -as far as AA powered lights goes - the TK41 is spectacular.

I'll speculate the "aberration" surrounding uneven patterns near the hot-spot have to do with slightly different wave-lengths of light arriving at the given surface in or out of phase, cancellation maybe?? (this at least explains why the pattern would change with distance)

Now I want to find the same performance in a 2x18650 torch. But if anyone wants an "AA" powered light the TK41 is your answer.

 

[xoomercom]

I already have the TK 40, and TK45 (missus loves it), I just ordered the TK 41.

Not much to say other than I love the fenix products. I'm impressed mostly with quality and output. Not to mention that I require AAs. I prefer the two button UI approach vs single clicker at the end. I'll post my take on it when it arrives.

 

[AusKipper]

I know I know, but am wondering how long a tk41 will actually last if its always in turbo. I'm thinking of getting one but would hate the guilty feeling when going exploring for a few hours in turbo

Even if it "only" lasts 25,000 hours because your using it in Turbo all the time, thats still about 3 years continuous

Something else will break by then (probably the switch) anyway.

I wouldn't worry about it.

 

[bbb74]

Even if it "only" lasts 25,000 hours because your using it in Turbo all the time, thats still about 3 years continuous

Something else will break by then (probably the switch) anyway.

I wouldn't worry about it.

I have the same question I've read Cree's lumen maintenance guide (which doesn't really cover XM-L's) and temperature (particularly ambient (the temp in the air around the led)) seems to be the biggest killer. I have to think when you drive the tk41 at 10 and a bit watts, that its going to be getting very hot inside when you compare it to a larger light fitting with lots of fins and stuff and that will reduce the life. I'm not sure what the life will be though... Would be curious to know what Fenix say about it, and how they've designed it to keep the led as cool as possible and what temps they've designed it to maintain.

 

[chenko]

Thanks for the great review, nice and useful information here! I just got my TK41 yesterday, it is superb and throws like no other lights I have experience of. It will be fun to amaze friends with it. My sample has good tint tough, some green is only visible in the hotspot's corona in the lowest setting, other settings all show a quite good cool white tint with a very slight bit of purple, which makes for a better cool type of tint overall. I'm kind of a tint snob, if those ever exist, and I usually only get flashlights in neutral or warm tint, but this tint seems acceptable to my eyes (if I don't directly compare to neutral ones, of course).

 

[todd.krock]

Hi HKJ and thanks for the review.

I recently purchased a TK41 and have a question regarding the beam profile.

My sample has a dark area where the hot spot should be which is encircled by a very bright ring before transitioning into the corona/spill.

This is ONLY noticeable beyond a distance of 4-5 meters. Any distance under that and the hot spot looks a normal solid white.

Here's a link to a video clip I took showing the effect:

http://www.mediafire.com/?qmc2mi2tpha07y2

This beam shot was taken at 20 meters.

Please note that the dark hot spot/bright ring effect was difficult to capture on camera and is much more apparent and obvious to the naked eye.

Does your TK41 sample exhibit this beam pattern?

I would like to establish if this is typical or if I have a defective unit. I have emailed Fenix but have received no response yet.

Feedback appreciated from any other TK41 owners.

I got my TK41 about a week ago. I notice the dark hot spot as you describe it as well. Please report back what Fenix has to say. Other then that this light is pretty darn awesome. The light still puts out and the ring is more of an annoyance then anything. But im sure it does effect the throw. Granite I'm an old maglight user myself, but WOW i guess anything would be brighter!

 

[HighLumens]

post deleted

 

[Sinsear]

I recently received my TK41 from BatteryJunction. I am noticing a very green ring around the hotspot on all brightness settings. In addition, I'm also noticing the doughnut effect on hotspot, even at considerable distance (it's obvious that there's going to be a doughnut effect when shining at a very close object, but I'd expect that to go away after 2 or so meters). Instead, at long distances, you can definitely make out that the center portion of the hotspot is less bright than the edges of the hotspot. FWIW, I also think that my LED is centered perfectly (although I don't think I've seen a flashlight that wasn't). Should I return my flashlight and exchange it out? I think the most bothersome aspect is the fact that there's a very defined green ring around the hotspot.

 

[louieg]

Waiting on my TK41 will let you know about green tinge and dark hot spot.

 

[burpee]

I was out "testing" my TK41 last night on bicycle trails in southern Illinois - no lights near area of testing. This map - shows where I could light up a 10 inch by 30 inch highway info sign mounted above a tunnel that runs under IL route 4. According to this mapping software the TK41 was "throwing" almost 1 mile! It took almost 4 minutes to ride up to the sign.

Click black and red "checker" for map notes.

 

[Nyctophiliac]

I was out "testing" my TK41 last night on bicycle trails in southern Illinois - no lights near area of testing. This map - shows where I could light up a 10 inch by 30 inch highway info sign mounted above a tunnel that runs under IL route 4. According to this mapping software the TK41 was "throwing" almost 1 mile! It took almost 4 minutes to ride up to the sign.

Click black and red "checker" for map notes.

That's a lot of throw! Do you simply stop and try out the light, or have you found a way to mount it on your bike? Any info gratefully received as I have been trying to mount my TK45 for ages and Duck tape seems to be the only option, but it ain't pretty! Or quick release!!

 

[samgab]

That's a lot of throw! Do you simply stop and try out the light, or have you found a way to mount it on your bike? Any info gratefully received as I have been trying to mount my TK45 for ages and Duck tape seems to be the only option, but it ain't pretty! Or quick release!!

Have you ever heard of, or tried, Twofish Lockblocks? I figure that even if you have to replace the velcro tape with a longer piece it could be jiggered to do the trick...
Also, I've found that even when pointing a fairly faint flashlight at reflective signs, they light up from very far away. But a mile is still impressive!

 

[todd.krock]

I got my TK41 about a week ago. I notice the dark hot spot as you describe it as well. Please report back what Fenix has to say. Other then that this light is pretty darn awesome. The light still puts out and the ring is more of an annoyance then anything. But im sure it does effect the throw. Granite I'm an old maglight user myself, but WOW i guess anything would be brighter!

Ok, I reached out to Fenix myself with a few beam shot pics and here is the response I received.

"I fully understand the phenomenon you mention according to the picture, this is normal phenomenon, because the light generated by the LED is not all reflected by the reflector, some is not reflected, if reflected by the reflector, the light brightness will be high, so the center beam which is not reflected seems a little darker comparatively.

This is common, and won't affect the normal use at all, this can be proved during your actual use in future."

Not sure I like the answer, but it is an answer none the less.

 

[burpee]

This is common, and won't affect the normal use at all, this can be proved during your actual use in future."

All lights that use a reflector will produce an uneven pattern at some point. The only way this could be avoided would be to have the reflector "meet" the very edge of the LED where light is generated, and even then you might get some uneven intensity.

Have you ever heard of, or tried, Twofish Lockblocks? I figure that even if you have to replace the velcro tape with a longer piece it could be jiggered to do the trick...

I made my own mount out inner tube rubber.

The trick is to fashion two rubber supports that form a "cradle" and then use additional rubber strips as rubber bands. I use two strips for security and firmness. I was using the TK41 on an unlit trail 30 miles east of Saint Louis. I could notice one "object" reflecting in the distant horizon.

The trail goes straight under IL route 4 in concrete box culvert of a tunnel. There is a standard style green and white highway sign, green background, reflective white letters and border. The sign is mounted to a concrete wall - 15-20 feet above trail/ground. There is no competing light - anywhere nearby.

I also use a folded piece of typing paper in the tube of the TK41 to dampen the battery carrier rattle. The TK41 was an experiment to examine how much "throw" is useful. It actually worked perfectly - although I doubt it is a good idea for mountain biking. The light was interesting to use because the spill was all out in front of me.

For a while I felt like I was in a locomotive cab lighting "rail trail."

 

[Samy]

My TK41 arrived today. I took it to work to test it out. In the the darkish areas around buildings and street lights the TK41 did not appear to be an "awesome" light. It was certainly brighter than my 200 lumen edc, but the beam appeared too centered for built up areas.

When I came home I tested it out in the rural forest setting where I live. It's very dark with no street lighting and the TK41 simply came alive. Comparing to my other lights there was a huge difference. The TK41 doesn't seem to do very long distances but anything within 100-300 meters is lit up very well. I compared my Klarus ST20 (200 lumens) to the TK41 and holding them the same, the TK41 has an almost identical spill but much brighter. This wasn't noticeable in and around the buildings at work but out in the forest it was clearly evident. The TK41 has some decent spill.

The other thing that suprised me is the excellent build quality and compact size. It does fit into my pockets

Cheers

 

[burpee]

I double checked the "throw" distance test i previously posted about. The TK41 will indeed light up a reflective sign a mile away. However, I do want to inform readers that most any light probably will do nearly the same. I tested the TK41 at the "medium" setting and found that there was a hint of reflection as well - at the 330 lumen rating.

It would be interesting for emergency professionals to have this same type of test performed - but use only the reflective surface of worker's safety vest as a reflector. In other words - test flashlights ability to find a piece of reflective clothing in a dark valley at 500 meters or more. That could be a useful test of beam character. Just saying....

 

[Fatso]

Great review and some awesome pictures!!
How does the TK41 compare to the TK60? The specs. are almost Identical.

 

[HKJ]

How does the TK41 compare to the TK60? The specs. are almost Identical.

I can not tell you yet. I already have the TK60 and have a TK70 on order, together with some other light. I plan on doing a "big lights" beamshot when they are arrives. I have not yet decided what ligths to include, but the TK41, TK60, TK70, SR51, SR90, SR91, SR92 and Blaster-NG will probably be included.

 

[Fatso]

The big gun's!!
I am currently trying to decide on getting either the TK70 or SR91 and been deciding for over two weeks now and still have no clue. I know the SR90 is a lot brighter than the SR91 but the TK70 has the lower levels that might come in handy.
I'm looking for more throw than flood so I'm thinking the SR91 or is it really worth spending $200 extra for the SR90?