[selfbuilt]

Warning: pic heavy, as usual.



By popular request, I have chosen to review the Fenix TK35 – a compact, high output XM-L-based light. Let’s see how it compares to the competition ...

Manufacturer's Specifications:

• LED: Cree XM-L
• Uses four 3V CR123A batteries (Lithium) or two 18650 rechargeable batteries (Li-ion)
• Six levels of output*]Turbo - 820 lumens, 1 hour 33 minutes
• High - 346 lumens, 5 hours 6 minutes
• Mid - 109 lumens, 16 hours
• Low - 12 lumens, 170 hours
• Strobe - 820 lumens
• SOS - 109 lumens
• Distance - 333m
• Intensity @ 1m - 27739cd
• Impact Resistance - 1.2m
• Waterproof Rating - IPX-8, underwater 2m
• Dimensions: Length: 164mm, Diameter: 43.64mm, Head Diameter: 51.5mm, Weight: 256g (excluding batteries)
• Digitally-regulated output, maintains constant brightness
• Reverse polarity protection, to prevent damage from improper battery installation
• Dual-button switch in tailcap for convenient operation
• Made of durable aircraft-grade aluminum
• Premium Type-3 hard-anodized anti-abrasive finish
• Toughened ultra-clear glass lens with anti-reflective coating
• Included Accessories: lanyard, holster, o-ring
• Estimated MSRP ~$110.

Packaging is typical for Fenix (i.e. cardboard box with molded plastic insert). Inside you will find the light, manual, warranty card, wrist lanyard, and belt holster.



From left to right: AW Protected 18650, TK35, Sunwayman M40C, Eagletac M3C4 XM-L, Fenix TK45, Lumintop TD15-X.

All dimensions given with no batteries installed:

TK35: Weight 256.1g, Length 162mm, Width (bezel): 48.6mm, Max Wdith 52.0mm
M40C: Weight: 258.5g, Length 156mm, Width (bezel) 57.1mm,
M3C4 XM-L: Weight: 348.0g, Length: 164mm, Width: 61mm (bezel)
M3C4 SST-50 SMO-Deep: Weight: 354.2g, Length: 165mm, Width: 61mm (bezel)
M3C4 SST-50 OP: Weight: 334.7g, Length: 158mm, Width: 61mm (bezel)

As you can see, the TK35 is one of the most compact offerings in this side-by-side 2x18650 class of lights.





The body plan of the TK35 is very streamlined, and quite comfortable to hold and handle.

Black anodizing (type III = HA) is matte finish, without blemishes on my sample. Lettering is clear and sharp, but not overly bright.

The light lacks knurling as such, but there are a series of tiny ridges along both sides of the battery handle (similar to the concentric ring ridges on the TK45). While this helps somewhat with grip, I still find the TK35 slipperier than other lights in this class.

Screw threads are square-cut and anodized, to allow for head lock-out.

Although it looks like it should, the light cannot easily tailstand, as the on/off switch bulges slightly on my sample (even when on).




The most unique aspect to the light is the battery compartment. Made entirely of plastic, it slides fully into the aluminum handle. Unlike the TK45, the springs used for positive and negative contact are on found on the head and not the carrier. The carrier chambers hold all my protected 18650 cells snugly, even the newer high capacity ones. There is a raised button at the positive terminal in each chamber, so flat-top cells work fine.

Probably the most distinctive thing about the barrier carrier is that it contains two different types of switches – a forward clicky for on/off activation, and a secondary electronic switch for mode changing, as described below.





The switch control mechanism is interesting. At the base of the body handle, you will see two buttons. The smaller of these is basically just a small plastic rod with a rubber top that serves as the mode changing button. When assembled, it makes contact with the actual electronic switch on the battery tube. There is a definite click when changing modes, but the feel is quite different from a traditional clicky.

The larger button is connected to a more traditional on/off clicky switch. Feel is a little stiffer than typical, but is otherwise familiar.

There is a definite rattle to light, even when fully assembled (likely due to the mode changing plastic rod). And you have to pay attention to how you insert the battery carrier – it only fits one way, due to the differing switch types.



The TK35 uses the Cree XM-L emitter, with a relatively deep and smooth reflector. There seems to be some very mild texturing applied to the surface, which slightly dulls the finish (likely to helps smooth the beam).

Which brings me to the white-wall beamshots. All lights are on 2xAW protected 18650, about ~0.75 meter from a white wall (with the camera ~1.25 meters back from the wall). Automatic white balance on the camera, to minimize tint differences.













First off, this sample has one of the most greenish tints I’ve ever seen. The pics above are all done with automatic white balance and are slightly desaturated, to minimize tint differences. In real life, it is more green than it appears above.

Beam pattern is actually very good – the light has a reasonable amount of throw, and a nice transition from spot to spill. I haven’t done outdoor beamshots yet, but those will be coming soon – check back in for updates!

User Interface

Turn on/off by the larger forward clicky switch (press-on for momentary, click for locked on).

Mode changing is controlled by the smaller secondary electronic switch. Click and release to advance through output modes, which proceed in sequence from Lo > Med > Hi > Turbo, in repeating sequence. The light has mode memory, and retains the last level set when you turn the light off and back on.

Note that you cannot set the output level while the light is off. The electronic switch only works when the light is powered on by the clicky switch first. As such, there is no standby current on the TK35.

The “hidden” strobe and SOS modes are accessed by clicking and holding the electronic switch for more than 1 sec. The light will now move between a slow SOS and a fast high intensity strobe when you click and release the electronic switch. To return to the constant out modes, hold the electronic switch for more than 1 sec again, or simply turn off/on the light.

The blinking modes also have a memory, and the light will return the last mode used when you re-enter this state – but the light always turns on in the memorize constant output mode. Thus, there is no danger of accidentally strobing yourself (but conversely, you cannot access strobe without first turning on the light in a constant mode).

The light has an interesting safety feature – after exactly 25 mins of continuous runtime on Turbo, it drops down to the Hi level for the rest of the time it is left on. Turning off/on restores the Turbo mode (at least for the next 25 mins ).

PWM/Strobe

There is no sign of pulse width modulation (PWM) on the Lo/Med/Hi modes that I can detect, leading me to conclude this light is current-controlled like almost all other Fenix offerings.



Strobe is an oscillating strobe, switching between 6.7 Hz and 15.9 Hz at ~1.8 sec intervals on my sample.

Testing Method:

All my output numbers are relative for my home-made light box setup, a la Quickbeam's flashlightreviews.com method. You can directly compare all my relative output values from different reviews - i.e. an output value of "10" in one graph is the same as "10" in another. All runtimes are done under a cooling fan, except for any extended run Lo/Min modes (i.e. >12 hours) which are done without cooling.

I have recently devised a method for converting my lightbox relative output values (ROV) to estimated Lumens. See my How to convert Selfbuilt's Lighbox values to Lumens thread for more info.

Throw/Output Summary Chart:

Effective November 2010, I have revised my summary tables to match with the current ANSI FL-1 standard for flashlight testing. Please see http://www.sliderule.ca/FL1... for a description of the terms used in these tables.



Output on max is very comparable to my other recent XM-L based lights, like the Eagletac M3C4, Thrunite Catapult V3 and Lumintop TD15-X. As expected, peak throw/beam distance is less than the larger M3C4 and Catapult V3 lights (with their larger and deeper reflectors), but is greater than the smaller TD15-X. Throw is basically in the traditional range of most of the larger SST-50-based lights.

Lo output is reasonable for this class – not as low as some earlier Fenix lights, but in keeping with most of the recent XM-L lights.

Output/Runtime Comparison:









I have only done 2x18650 runtimes, but the light can also handle 4xCR123A. As you can see, output/runtime efficiency is certainly in keeping with other current-controlled lights with XM-L emitters – and perhaps even a touch better on my TK35 sample.

You will also note the interesting runtime pattern on Turbo. After exactly 25 mins, the light drops to Hi for the rest of the run (i.e. the first TK35 trace on my Max 18650 graph). This is not a thermal sensor, but a timed drop-down feature. To allow you to better compare to other lights that remain constant, I flashed the TK35 off-on every 20 mins in the second run, so you can see what happens if you keep it going (i.e. labelled as "*restarts*" in the first graph legend).

Potential Issues

As always, I have some concerns over long-term stability with any all-plastic battery carrier. Although the TK35 carrier seems better than their previous offerings in the high-output class, the dual switch control area feels relatively cheap. In particular, the simple plastic plunger that connects to electronic switch does not inspire a lot of confidence (it also rattles at all times).

The heavily green tint on my sample suggests that Fenix is using non-premium cool white tints for this line. This would be in keeping with the lower than typical price.

Light lacks any real knurling, and can be more slippery than most in this class.

Holster and wrist lanyard are fairly basic, but at least they are both provided (which is more than some manufacturers).

Preliminary Observations

In many ways, the TK35 is something of a Goldilocks model. Build-wise, you could argue that most of the other high-output lights are either too long, too thick, too heavy, or too light. The TK35 feels just about right in the hand – nice and compact, and well-balanced.

Same goes for the beam pattern. No, it is not a huge thrower for the XM-L class – but it throws as well as the much larger SST-50-based lights, and better than all the earlier MC-E ones. No, it doesn’t have a huge spillbeam width, like lights with massively wide heads. Instead, it has a very well balanced beam profile that suits most general uses.

I think the dual control interface is generally well implemented. You can easily use the light in over-hand tactical grip without having to re-position (i.e. buttons are easy to differentiate). I would have liked to have been able to set the output level before activation, but that would have required a major redesign (and likely necessitated a standby current drain in this dual switch setup).

Of course, one area where you can always expect Fenix to excel is in overall output/runtime efficiency. No surprises here – the TK35 does as well (and perhaps slightly better) in overall efficiency as any other current-controlled light in the XM-L class. The 25 min drop-down feature on Turbo is interesting (and likely a good safety feature), but you can always circumvent it if you need to by turning off/on again. And max output is consistent with all the recent XM-L lights I’ve tested.

Another distinctive feature of the TK35 is the price. I don’t normally comment on this in my reviews, but it is remarkably low considering everything you are getting here (i.e. ergonomics, performance, and the reassurance of an established brand name).

So, with all that going for it, sounds like slam-dunk right? Well, not necessarily. That low cost brings a few less desirable aspects with it. As mentioned above, I don’t like all-plastic battery carriers (although this one is better than most). But I do find the switching control area has a rather cheap feel, and I worry about its long-term stability.

The other cost issue is tint. There are never any guarantees here – but some makers do pay extra to insure specific “premium” cool white tint bins are used. In my experience, Fenix doesn’t typically do this (although to be fair, they are also a much higher volume manufacturer, and therefore have to go with what’s available). I bring this up only because my TK35 sample has the most greenish tint that I’ve ever seen in all my flashlight testing. What this suggests to me is that you can therefore expect a very wide range of possible tints on the TK35 – caveat emptor.

And although I like the body design (and the nice touches like anodized square threads, etc.), I would also like to see some actual knurling on the light to improve grip. Probably one of the best builds I’ve seen in this size light is the Sunwayman M40C – an even more compact side-by-side 2x18650 design, dual interface with magnetic control ring, all-metal carrier, etc. But it uses the older MC-E emitter and as is still ~50% more expensive.

At the end of the day, I think the TK35 is a fantastic bargain with a good overall design, good mix of features and outstanding performance. The build is still not quite everything it could be, but it is certainly still quite acceptable - you just need to have realistic expectations for the price. And honestly, I don’t see how you could do much better at this price point for a high-output light, at the current time.

UPDATE MAY 13, 2011: I have just reviewed the JetBeam BC40 - an even less expensive 2x18650-class XM-L light. It has a simpler two-stage output UI, but is something else to consider in the "budget" high-output class.