The Sofirn SP35 flashlight is now available with advanced temperature regulation (ATR). Read on for testing on this high output flashlight!
Official Specs and Features
Notably there are two versions – the ATR version, and the older version which doesn’t have thermal regulation.
As far as bodies, it looks like just the black body option. And finally emitters – there are two temperatures: 5000K and 6500K (seen here).
The complete package on amazon is $40. That includes the 21700 cell, which makes it a complete package. Now, I wouldn’t pick 6500K but that’s what amazon has, and so this seems like a pretty solid deal. Here’s an amazon referral link.
The Sofirn SP35 ATR flashlight is a pretty cool light. The 6 stepped modes are great – low is low and high is high, and there’s plenty between. If you don’t like stepped, there’s ramping too!! The price is great!
The Big Table
|Sofirn SP35 (ATR) Flashlight|
|Emitter:||Luminus SST-40 (6000-6500K)|
|Price in USD at publication time:||$31.99|
|Turbo Runtime Graph||High Runtime Graph|
|LVP?||Switch warning, then off.|
|Quiescent Current (mA):||0.02|
|Charge Port Type:||USB-C|
|Power off Charge Port||With cell: All modes
Without cell: Lowest 4 modes
|Claimed Lumens (lm)||2000|
|Measured Lumens (at 30s)||1633 (81.7% of claim)^|
|Candela per Lumen||14.6|
|Claimed Throw (m)||332|
|Candela (Calculated) in cd (at 30s)||1069lux @ 4.81m = 24732cd|
|Throw (Calculated) (m)||314.5 (94.7% of claim)^|
|All my Sofirn reviews!|
^ Measurement disclaimer: I am an amateur flashlight reviewer. I don’t have $10,000 or even $1,000 worth of testing equipment. I test output and such in PVC tubes!! Please consider claims within 10% of what I measure to be perfectly reasonable (accurate, even).
- Sofirn SP35 ATR flashlight
- Sofirn 5000mAh 21700
- Charge cable (USB to USB-C)
- Spare o-rings (2)
Package and Manual
Build Quality and Disassembly
For $40, this Sofirn SP35 ATR flashlight has superb build quality. Really, even for more money this would be a reasonable light. Nothing is noteworthily bad regarding the build. In fact, there are many things to really like here!
Here’s the top-down view. Maybe I’m getting better at this….
Here on the head are some cooling fins. They’re not incredibly deep, but you wouldn’t expect them to be on a tube light.
The tailcap is surprisingly bare – this light seems to want to be a dual switch light, but there’s just the e-switch. I like it very much in this setup, though.
Both the head and tail come off the cell tube.
Threads here are great, too – square cut, anodized, and well lubed. They’re quite long.
The head end has the same threads.
A very thick beefy spring graces the tailcap, and the whole piece is held in by a retaining ring.
No spring is on the head end, just some brass contact rings.
Like I said above, the threads are the same on both ends. This means the cell tube is reversible – you’ll see later why that’s good.
Size and Comps
Dimension: 126mm (length) × 28mm (head diameter)
Weight: 73 grams (without battery)
If a light will headstand, I’ll show it here (usually the third photo). If a light will tailstand, I’ll show that here, too (usually the fourth photo).
Here’s the test light with the venerable Convoy S2+. Mine’s a custom “baked” edition Nichia 219b triple. A very nice 18650 light.
And here’s the light beside my custom engraved TorchLAB BOSS 35, an 18350 light. I reviewed the aluminum version of that light in both 35 and 70 formats.
This is just a fun joke photo – cell tube is gone, with the head atop the tail.
Retention and Carry
A lanyard is included, and attaches through a hole in the tailcap as seen below.
Only one side has the lanyard hole. It’s just one hole, too, and so when tailstanding the lanyard will get in the way just a little bit. It’s very thin though, so that’s not the biggest problem.
A pocket clip is included, too.
This clip is designed to attach in only one place on the cell tube. By default that is on the tail end, but since the cell tube is reversible, you can set the light up as a “bezel up” carry if you wish.
It’s a “pretty deep” carry clip, especially with the overall size of the light.
There’s no pouch or magnet or anything else.
Power and Runtime
The Sofirn SP35 ATR flashlight is a single lithium-ion cell light. The cell tube is 21700 sized, and that’s the cell which ships in the package.
This is a flat top unprotected 21700. Other type 21700 cells should work with no issues in the Sofirn SP35 ATR flashlight.
The cell is installed into the Sofirn SP35 ATR flashlight in the usual way – positive end toward the head.
Below you can see a few runtime tests. The ATR feature – Advanced Temperature Regulation – of the Sofirn SP35 ATR flashlight can be readily seen after the initial stepdown. The output is extremely active in managing the temperature around 40 degrees Celsius. The setting isn’t something that can be changed. (Being able to change this to 50°C or so would be great!)
It really seems that Turbo is the only mode that requires ATR – temperature on High and lower never really gets unmanageable at all.
In all tests the Sofirn SP35 ATR flashlight turns off after a switch warning.
Built in to the Sofirn SP35 ATR flashlight is USB-C charging. This is a nice “current generation” charging method (better than micro-USB).
The charge port is in the head, just opposite to the switch. These two items (switch and charge port cover) are different enough that you’ll not confuse them.
Sofirn includes a charge cable – USB to USB-C. It’s a surprisingly high quality cable. I tested operation with USB-C to USB-C and that works (but looks to just be at 5V). Still, it works, which is good.
Here’s a charge graph – I logged only with USB to USB-C, since that’s the cable Sofirn supplies. Charging is very good – around 2A at a peak, and fills the cell to around 4.15V. When topped off in a bay charger, the cell took only around 50-60mA more (ie, practically negligible).
While charging, the indicating switch will be flashing red. When charging is complete, the switch will turn green.
Modes and Currents
|Mode||Mode Claimed Output (lm)||Claimed Runtime||Measured Lumens||Tailcap Amps|
Pulse Width Modulation
There’s no PWM on any mode. There’s a little sawtooth on one mode, but this isn’t visible.
For reference, here’s a baseline shot, with all the room lights off and almost nothing hitting the sensor. Also, here’s the light with the worst PWM I could find. I’m adding multiple timescales, so it’ll be easier to compare to the test light. Unfortunately, the PWM on this light is so bad that it doesn’t even work with my normal scale, with is 50 microseconds (50us). 10ms. 5ms. 2ms. 1ms. 0.5ms. 0.2ms. In a display faster than 0.2ms or so, the on/off cycle is more than one screen, so it’d just (very incorrectly) look like a flat line. I wrote more about this Ultrafire WF-602C flashlight and explained a little about PWM too.
User Interface and Operation
The Sofirn SP35 ATR flashlight is controlled by a single switch. It’s an e-switch on the side of the head.
This switch also has indicating features – below it’s seen indicating red for low voltage. Notably, the switch will indicate for 5 seconds after the light is turned on, as follows:
Green: remaining battery power is good
Red: remaining battery power is poor (less than 30%)
Red Flashing: recharge or swap cell immediately.
There’s a surprising amount of travel on this switch. It’s also quite proud
Here’s a UI table!
|Off||Click||On (Mode Memory)|
|On||Hold||Group 1: Mode cycle (Eco, Low, Medium, High only)
Group 2: Ramp up
|Any (except Turbo)||Double Click||Turbo|
|Turbo or Strobe||Click||Previous state|
|On||Click 4x||Switch between Group 1 and Group 2|
|Strobe||Double Click||Strobe advance (Strobe, Beacon, SOS)|
|Lockout||Click||Main emitter blink 2x to indicate lockout|
Why you’d want to double click from Turbo to get to Moonlight, I have no idea.
Group 2 (Ramping) is very similar to the above Group 1, except holding the switch will cause the light to ramp up. Loosening then holding the switch again within 1.5s will cause the ramp to switch directions. So it’s possible to ramp up or down. Double click still gets Turbo.
LED and Beam
In my review copy of the Sofirn SP35 ATR flashlight is a Luminus SST-40 emitter, in 6500K. This emitter is surrounded by a smooth and quite deep reflector.
The bezel has some shape, so when headstanding some light can escape.
Check out the smooth reflector!
Maybe mine’s 6500K, but I have to say it’s still a clean beam, and doesn’t feel so much like 6500K. Warmer than 6500K.
These beamshots are always with the following settings: f8, ISO100, 0.3s shutter, and manual 5000K exposure.
Tint vs BLF-348 (KillzoneFlashlights.com 219b version) (affiliate link)
I keep the test flashlight on the left, and the BLF-348 reference flashlight on the right.
I compare everything to the KillzoneFlashlights.com 219b BLF-348 because it’s inexpensive and has the best tint!
What I like
- Great deal at $40.
- Good beam profile
- Throw is good
- Ramping option if you want it…
- But the stepped group is very smart too
- USB-C charging works great
- No PWM
What I don’t like
- I wish the switch was just a little lower to the body – it sits a bit too proud
- Ramping is a little bit awkward with ramp speeds
- This light was provided by Sofirn for review. I was not paid to write this review.
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