Sofirn SK40 Tactical Flashlight Review
The Sofirn SK40 tactical flashlight offers a Luminus SFT-70 emitter. There’s a mechanical switch and a side e-switch. Output is fantastic and throwy! Read on.
Official Specs and Features
Here’s a link to the Sofirn SK40 tactical flashlight product page.
Versions
There appears to be just one version of the Sofirn SK40 tactical flashlight.
Price
The Sofirn SK40 tactical flashlight sells for $45.99. The price includes the 21700. Very nice!
What’s Included
- Sofirn SK40 tactical flashlight
- Sofirn 5000 mAh 21700
- Charge cable
- Lanyard
- Spare o-rings (2)
- Manual
Package and Manual
Build Quality and Disassembly
Many Sofirn lights have designs and build quality similar to that of this SK40 tactical flashlight. Sofirn makes nice lights, particularly for the (low) price.
The Sofirn SK40 is designated as a tactical flashlight, and it has dual springs to support that idea. They’re nice and beefy, too!
It’s a bit hard to tell in this photo, but the cell tube is not reversible. The head end is a good bit bigger in diameter than the tail end.
Size and Comps
Size: 40mm x 146.5mm
Weight: 132g(without battery)
If the flashlight will headstand, I’ll show it here. If the flashlight will tailstand, I’ll also show that here too!
Here’s the test light with the venerable Convoy S2+. The version below is a custom laser-engraved Convoy S2+ host by GadgetConnections.com. I did a full post on an engraved orange host right here! Or go straight to GadgetConnections.com to buy your Convoy S2+ now!
In the photo above, you may note that the SRM (standard reference material) flashlight for comparison has changed! I used a TorchLAB BOSS 35 for ages. Now what you can see as the 18350 SRM is the Hanko Machine Works Trident. While I have not reviewed or tested the Gunner Grip version seen here, I have tested a Hanko Machine Works Trident Total Tesseract in brass. I love the Trident, and it’s a striking contrast next to the inexpensive Convoy S2+, which also makes a great standard reference material.
Retention and Carry
The first line of carry is the pocket clip, which isn’t reversible. Friction fit, and allowing only bezel down carry. Because of the head size, this clip is probably more of a “belt” clip than a pocket clip.
The second option is the lanyard, which attaches to the tailcap. It’s also possible to connect it on the pocket clip, but I’d stick with the tailcap.
Power and Runtime
The SK40 is powered by a single lithium-ion cell. Sofirn includes a Sofirn branded 5000mAh 21700, which was used for all testing of this light. Since the light has springs on both ends, any type 21700 should work just fine (provided it’s not too long).
The cell goes into the Sofirn SK40 tactical flashlight in the usual orientation – positive end toward the head. In case you forget that, the tailcap has a little icon.
Runtimes are below. There are three of them – the highest three levels. Performance looks pretty good on high and lower, but Turbo steps down at around 30 seconds.
In each case, the switch indicated when the cell voltage was low and then the light shut off.
Charging
The Sofirn SK40 tactical flashlight also offers built-in charging by way of USB-C charging port in the head end.
I managed to miss getting a photo of the charge port open, but the cover is a standard press-in fitting.
Sofirn includes a USB-C to USB-C charging cable.
Charging isn’t especially quick and doesn’t terminate too cleanly – the charging just trails off. The cell doesn’t get overcharged though, so that’s fine. And also, charging is essentially complete after around 4 hours at most.
Modes and Currents
| Mode | Mode Claimed Output (lm) | Claimed Runtime | Measured Lumens | Tailcap Amps |
|---|---|---|---|---|
| Turbo | 3200-1100 | 1m+1h50m | 2400 (0s) 2354 (30s) |
11.70 |
| High | 1500-1100 | 5m+2h10m | 1189 (0s) 1178 (30s) |
3.25 |
| Medium | 500 | 4h50m | 471 | 0.97 |
| Low | 150 | 18h | 141 | 0.24 |
| Eco | 10 | 290h | 5.7 | [low] |
Pulse Width Modulation
None of the five modes use PWM. Yay!
Here you can see a “baseline” – a chart with almost no light hitting the sensor.
Then there’s the Ultrafire WF-602C flashlight, which has some of the worst PWM I’ve seen. It’s so bad that I used a post about it to explain PWM! Here are multiple timescales (10ms, 5ms, 2ms, 1ms, 0.5ms, 0.2ms) to make comparing this “worst” PWM light to the test light easier. That post also explains why I didn’t test the WF-602C at the usual 50us scale.
User Interface and Operation
There are two switches on the Sofirn SK40 tactical flashlight. The tail switch is mechanical forward clicky. The dome on the switch is big and grippy but does not protrude enough to prevent tailstanding.
The other switch is on the head and is an indicating e-switch. It’s nicely clicky and has very good action. The indicator in the center of the switch can be red or green.
One notable thing about the indication on that switch is that it indicates the battery charge level for 5 seconds every time the tail switch is turned on.
Here’s a user interface table! There are two modes – Duty mode (default) and Tactical mode. Below is the table for Duty mode. Everything is the same between the user interfaces, except where noted in the table.
| State | Action | Result |
|---|---|---|
| Off | Click Tail Switch | Duty Mode: On (Mode Memory) Tactical Mode: Turbo |
| Off | Half press + click | Duty Mode: Turbo Tactical Mode: Strobe |
| Off | Click Side Switch | No Action |
| Off | Half-press Tail Switch | Momentary (Mode Memory) |
| On | Click Tail Switch | Off |
| On | Click Side Switch | Duty Mode: Mode advance (ascending, LMH) Tactical Mode: Mode advance (Turbo, Medium only) |
| On | Duty Mode: Click Side Switch 3x Tactical Mode: Click Side Switch 2x |
Strobe |
| Strobe | Click Side Switch 2x | Strobe Group Advance (SOS, Beacon, Strobe) |
| Strobe | Hold Side Switch | Return to the previous steady mode |
| On | Double Click Side Switch | Iterate between Turbo and Eco |
| Off | Hold Side Switch and click tail switch | On in Eco |
| On | Hold Side Switch 3s | Iterate between Duty and Tactical Groups |
That’s really a pretty simple dual-switch user interface. I like it too, because everything makes pretty good sense, and is intuitive. The strobe is also not too in the way.
LED and Beam
The Sofirn SK40 tactical flashlight uses a Luminus SFT-70 emitter. I don’t see this information on the box but it appears to be a 6500K version. There’s a nice deep reflector to go along with the throwy emitter, too!
LED Color Report (CRI and CCT)
The CCT is cool on the lower modes and gets cooler as driven harder on the higher modes. CRI is low, at around 70. These are reasonable specifications for a tactical flashlight, being driven at >10A on turbo.
Beamshots
These beamshots always have the following settings: f8, ISO100, 0.3s shutter, and manual 5000K exposure. These photos are taken at floor level, and the beam hits the ceiling around 9 feet away.
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. These photos are taken around 18 inches from the door.
I compare everything to the KillzoneFlashlights.com 219b BLF-348 because it’s inexpensive and has the best tint!
Summary and Conclusion
The Sofirn SK40 tactical flashlight offers great output and a robust tactical build at a reasonable price. The user interface is simple but offers a couple of mode groups, so you can probably get what you want. You can even get to Eco mode from off! USB-C charging works fine.
The Big Table
| Sofirn SK40 tactical flashlight | |
|---|---|
| Emitter: | Luminus SFT-70 |
| Price in USD at publication time: | $45.99 |
| Cell: | 1×21700 |
| Runtime Graphs | |
| LVP? | Yes |
| Switch Type: | Both |
| Quiescent Current (mA): | – |
| On-Board Charging? | Yes |
| Charge Port Type: | USB-C |
| Charge Graph | |
| Power off Charge Port | – |
| Claimed Lumens (lm) | 3200 |
| Measured Lumens (at 30s) | 2354 (73.6% of claim)^ |
| Candela per Lumen | 42.18 |
| Claimed Throw (m) | 580 |
| Candela (Calculated) in cd (at 30s) | 2790lux @ 5.699m = 90615cd |
| Throw (Calculated) (m) | 602.0 (103.8% of claim)^ |
| Claimed CCT | 6500 |
| Measured CCT Range (K) | 6100-7400 Kelvin |
| Item provided for review by: | Sofirn |
| All my Sofirn reviews! | |
^ Measurement disclaimer: Testing flashlights is my hobby. I use hobbyist-level equipment for testing, including some I made myself. Try not to get buried in the details of manufacturer specifications versus measurements recorded here; A certain amount of difference (say, 10 or 15%) is perfectly reasonable.
What I like
- Build quality
- Reasonable cost
- User interface has multiple groups
- Hits throw claim of 580m
What I don’t like
- Low CRI
- High CCT on highest modes
Notes
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