Overview:

This is a very nice budget 4AA light.  Competes with single cell Li-ion lights in power.  Has good mode spacing and pretty nice user interface ("UI").  It's compact, light in weight, and feels great in hand.  Very useful general-usage beam pattern that tends towards throw.  Very nice white with no obvious tint.

This light was provided to me by ThorFire for review.  ThorFire has not tried to influence the review.  There have been a couple BLF reviews as follows (In order of BLF Screen Name):

• RobertB
• tru3s1lv3r

Pros:

• Powerful (1100 lumens rated, 1200+ lumens measured)
• Good number of modes and separation
• Very well machined and finished.  Squarish cut threads
• Great heat sinking
• Feels great in hand with grippy knurling
• Side-switch with battery charge indicator
• Hidden, but readily available Strobe
• Tail stands real good
• Well regulated driver
• Nice UI overall

Cons:

• Thread Locked Head (both at the bezel and battery tube)
• Would like Moon Light mode to be about a quarter of a lumen brighter and Low Mode to be about 5 to 10 lumens less
• There is one occasionally frustrating issue with the UI (see below for details)
• Unlubed tailcap threads.  Feels very scratchy, but gets better with lube and usage
• No stainless steel bezel (But not expected at this price range)

UI:

Press the switch to turn on.  Presses while on change brightness levels from Low-Medium-High-Turbo.  Has last used mode memory.  Brightness level changes are a bit delays, but not obnoxiously slow.  A double click to activates Strobe, another click goes back to the previous brightness level.  While On, a press and hold turn the light off.  When the light is Off, a press and hold (about 1 second) activates Moonlight mode, an additional click turns the light off.  Turbo times out at 3 minutes.  Steps down to High mode.

Per the manufacture, the battery indicator displays “Green” when battery capacity is higher than 60%, Orange below 60% and over 15%, then Red when less than 15%.  I didn't test this, but it has appears to operate properly in my experience to date.

There is one frustrating issue I have with the UI.  The combination of the slow mode changing, the requirement to have to march forward through the mode levels, and easily triggered switch can become annoying at times.  It happens when the button is accidentally pressed which is easy to do.  To get back to the mode you were in, you are forced to progress through some very bright modes at a slow rate.  Ruining your night vision and maybe getting unwanted attention (like when indoors or camping with other people).  I guess it could be improved by making it possible to step backwards in mode level.  Maybe stiffen the button slightly too.

Performance:

My output measurements differed from the specs but all in good ways.  I'm still working on my light tube, but I think my measurements are in the ballpark of reality.  I'm pretty sure my intensity measurement (taken by a HS1010A at 10ft and calculated back to 1 meter) are as good as the meter can provide.  Most notably, I measured High at 420 lumens (rated at 600) and Turbo at 1200+ lumens (rated at 1100).  These are good news as the mode separation is good and high is great for a 4AA.  I measured intensity (throw) at 24.5kcd (rated at 11.6kcd).

Calculated lumens are roughly estimated from chart in Dozz's XPL V6 test thread.   Two huge caveats is that we don't know the bin of the emitter and how much current is actually making it to the emitter.  So it's hard to assess the reasonableness of the above measurements.

Temp and lumen measure measurement through 3 Turbo time outs.  Had an interruption which delayed reactivation of second Turbo by about 35 seconds, but it's clear that the light regulates output and manages it's heat well.  No signs of output sagging due to heat.  Light was 118.4F (48C) at the end of three Turbo time outs (9 minutes cumulative).

Blue Line = Lumens

Red Line = Temperature in Fahrenheit

Comparison and Tear Down Pictures:

The TK4A is smaller than all my other 4AA lights.  These below are the most like it in format.  It appears the the TK4A is not lined up well with the others.  The light is slight narrower than the other, but the placement in the first picture below exaggerates it slightly.

 Really nice reflector and lens:

I don't have much in the way of tear down pics.  The light is thread locked real good.  My attempts to open it were unsuccessful.  I only heated it to about 300F as I don't know what inside might melt in the process. The whitish residue in the second picture is from coconut oil.  The threads were so scratchy, I couldn't stop myself from slathering it all over the threads.  Got carried away and some got on the alignment posts.

Beamshots:

Been having a hard time getting good conditions for outdoor shots.  Pine pollen hit early this year.  It seems to suck some of the light out of the beam.  Too me, the actual light output is brighter than the below pics.  Especially, the bottom throw shot to the tall pine tree (about 250 feet away and over 70 feet tall).  I will try to redo the beam shots when conditions are better.

 Conclusion:

I like this light a lot.  I think ThorFire should consider a slightly floodier version of this light, upping Moonlight Mode slightly, decreasing Low Mode slightly, and adjusting the UI as discussed above.  Another plus of a floodier version is that the length could be decreased for an even more compact light.  Of course, I personally wish they would not thread locker or at least use a weaker (lower temp) thread locker.  This one is locked down tight. 

ThorFire has offered a 20% off coupon code for the TK4A flashlight: EHSQSZAA.

I'll make another attempt to open up the light and hopefully get some current to the emitter and driver efficiency measurements.  If I do, I will report back.