Sofirn SC33

The SC33 is a high-output, general-purpose flashlight running on a single included rechargeable 21700 battery. It features a well-regulated and efficient boost circuit for maximum performance.

  1. Introduction
  2. Manufacturer Specifications
  3. Package Details
  4. Build
  5. User Interface
  6. Circuit Measures
  7. Emitter Measures
  8. Beamshots
  9. Testing Results
  10. Runtimes
  11. Pros and Cons
  12. Overall Rating
  13. Preliminary Conclusions
  14. Acknowledgement


I’m still catching up on my backlog – this SC33 sample was received at the end of last summer.

Following the release of the popular Wurkkos TS22 earlier last year, there was much interest in the enthusiast community to see a similar model with auto-lockout disabled. Wurkkos’ sister company Sofirn didn’t take long to come out with the SC33 to meet this need.

The SC33 features the Cree XHP70.3 HI emitter (which the TS22 was eventually upgraded to as well), available in both the neutral-white 5000K and cool-white 6500K tints. You can also get it as a kit with a Sofirn-branded 21700 included.

Let’s see how it performs in my testing.

Manufacturer Specifications

Note: As always, these are simply what the manufacturer provides – scroll down to see my actual runtimes.

EmitterXHP70.3 HI
Tint5000 K
Max Output (Lumens)5,200
Min Output (Lumens)10
Max Runtime300 hours
Max Beam Intensity (cd)26,750 cd
Max Beam Distance (m)327 m
Constant Levels6
FlashingStrobe, SOS, Beacon
Weight (w/o battery)110 g
Weight (with battery)-
Length131 mm
Head Diameter32 mm
Body Diameter-

Package Details

The SC33 came in the modern “cellphone box” style packaging common for higher-end Sofirn and Wurkkos models. Included:

  • Sofirn SC33 flashlight
  • Sofirn-branded 5000mAh 21700 battery
  • Pocket clip (attached by three hex screws)
  • Wrist lanyard
  • USB-C charging cable
  • 2 Spare O-rings
  • Manual

It’s a decent package for a “budget” build, but I would like to see a holster included.


From left to right: Wurkkos 21700 (5000mAh), Vapcell 21700 F56 (5600mAh), Emisar D4K, Wurkkos WK15, Armytek Wizard C2 Max, Wurkkos TS22, Sofrin SC29, Speras E21, Wuben X1 Falcon, Sofirn SC33, Sofirn SP35T, Cyansky P50R, Cyansky P25.

The SC33 is considerably heftier than the TS22 – the handfeel is quite noticeably different. From the pics alone, you might think this is a compact light – it is actually one of the most beefy electronic-switch controlled 1×21700 lights I’ve tested. This is a key discriminating factor to keep in mind, if you looking at the choosing between models.

While it is not as long as the Sofirn SP35T (with its physical tail clicky), the SC33 is heavier. Like the earlier Sofirn light, thie SC33 features a dual spring design. This makes the light very suitable for tactical purposes, but it does mean you have to accept greater length.

The SC33 is a distinctive build – most notable for the charging port in the tail and attached pocket clip. I’m not sure why they went this route for charging, since it also necessitates a dual-body wall design for the current path. This explains the greater width of the SC33.The charging port has a built-in rubber dust cover. This should provide decent splash-resistance, but I wouldn’t recommend dunking the light in water.

The pocket clip is affixed by 3 small hex screws. The clip is thus removable, but not something to swap on or off easily. Note it only positions the light in a single direction (i.e., bezel down). So it wouldn’t be suitable to mount on a ball cap, for example.

The electronic tailcap switch has a metal cover with circular ridge detail. I found the switch traverse and performance consistent with most modern electronic switches – a bit soft, but decent enough. It is a slightly audible click. Given the switch cover’s slightly recessed nature, it is able to tailstand stably (although is still near enough the surface that accidental activation is possible).

Body threads at the head are square-cut but not anodized – again, another aspect required by the tail charging feature. A physical lockout is not possible on this light, you will need rely on the an electronic lockout.

The SC33 uses a concentric ring design on the body, with some additional cut-outs, to help with grip. With the included clip installed, I would say grip is excellent. Also thanks to included clip, the light will not roll when layed on its side. Anodizing looks to be good quality, with no damage on my sample. I would describe the finish as matte.

Inside, the light comes with a Sofirn-branded standard-sized 5000mAh 21700 battery, with a slightly raised flat-top. There is a good size spring in the head, ensuring good contact.

There is a small LED at the base of the head, that shows the charging or battery charge status (scroll down for details).

This is a very solid light, with good grip and handfeel. But it is more substantial than most in this class, which also makes it less “pocketable”.

The SC33 comes with a Cree XHP70.3 HI emitter, which is my preferred high-output choice (due to the reduced colour aberrations compared to the HD emitters). The reflector is fairly deep and heavily textured (heavy orange peel, HOP). There doesn’t seem to be any kind of anti-reflective coating on the lens.

The bezel is crenelated aluminum. Scalloping is not too aggressive, but would do some damage if you struck someone with it. Light can headstand stably.

User Interface

The SC33 uses a straightforward user interface, and one that is very similar to the Wurkkos TS22.

To start, you have a choice between Stepped Ramping mode (default), or continuously-variable Smooth Ramping mode. To switch between these modes, click 4 times when the light is On.

Stepped Ramping mode (default) levels: Moonlight, Eco, Low, Mid, High, Turbo, Strobe, SOS, and Beacon.

From OFF:

  • Press-and-hold: Turns on in Monlight mode.
  • Single-click: Turns On in last memorized mode.
  • Double-click: Turns On in Turbo (or, if auto-lockout engaged, turns On in the last memorized mode).
  • Triple-click: Turns On in Strobe.
  • 4 clicks: Activates Lockout mode. Double-click to unlock and return to memorized mode.

From ON:

  • Press-and-hold: Advances through main output modes.
  • Single-click: Turns Off.
  • Double-click: Jumps to Turbo. Single click returns to last memorized mode.
  • Triple-click: Jumps to Strobe.
  • 4 clicks: Switch between Stepped Ramping mode and Smooth Ramping mode.

From Lockout:

  • Press-and-hold: Momentary Moonlight mode, until you release
  • Single-click: Nothing (does a double flash to show lockout status)
  • Double-click: Turn on in last memorized mode.
  • 4 clicks: Disable Auto-Lockout.

Mode memory:

Yes, for constant output modes.


  • Moonlight mode: Press and hold the switch.
  • Turbo mode: Double-click the switch from On or Off.

Battery indicator:

When first activating the light, the indicator on the side switch shows the battery capacity remaining (lasts for ~5 secs upon activation):

  • Solid green: ~75-100%
  • Flashing green: ~50-70%
  • Solid red: ~25-50%
  • Flashing red: 0-25%

Low voltage warning:

Yes, the main light will step down as the battery is running low. It will then turn Off at ~2.95V

Lockout mode:

No physically, only electronic lockout. Enabled by default, auto-lockout can be disengaged.

Reviewer Comments:

I find this interface fairly intuitive, with a click to turn On in constant output modes, and press-and-hold for Moonlight (from Off). Otherwise, press-and-hold advances modes, single click turns Off/On, and shortcuts/blinky modes are multiple clicks. This is the most common arrangement, and works well. And you have the choice of smooth ramping or stepped, which is appreciated.

Like most enthusiasts, I’m not a fan of auto-lockouts, so it’s nice to have the option to disable it here. But I should note that auto-lockout is engaged by default.

Circuit Measures

No Pulse-Width Modulation (PWM):







There is no sign of PWM, the circuit appears to be fully current-controlled. There is no circuit noise on any level. This is similar to the TS22, except that model showed some (non-visible) high-frequency circuit noise on Turbo.

Note that circuit noise is not a concern, as it common to many lights. But do find that its absence (as in this case) bodes very well in terms of regulation and output/runtime efficiency. Scroll down to see actual results.



Strobe alternates between 8 Hz and 14 Hz every ~2 secs or so. Very disorienting and distracting.


A standard SOS mode, relatively slow.


A single flash beacon once every 2 secs (0.5 Hz).


There is a small LED in the head which shows solid red when the light is charging. Changes to solid green when the charging is complete.

Resting voltage <3.0V

Resting voltage >3.0V

The SC33 has a two-stage charging feature, as seen on many modern lights (i.e., where there is a lower initial charging rate when the cell is heavily discharged). The initial charging rate here is ~0.3A, which jumps to ~1.5A once the cell is over 3.0V resting voltage. This is a decent charging rate for the class, and will charge a 21700 cell quickly.

Standby / Parasitic Drain:

Due to electronic switch, there is bound to be a parasitic standby drain when the light is not in use. But because of physical build, I wasn’t able to measure.

Emitter Measures

In this section, I directly measure key emitter characteristics in terms of colour temperature, tint, and colour rendition. Please see my Emitter Measures page to learn more about what these terms mean, and how I am measuring them. As tint in particular can shift across levels, I typically stick with the highest stably regulated level for all my reported measures.

As explained on that page, since I am using an inexpensive uncalibrated device, you can only make relative comparisons across my reviews (i.e., don’t take these numbers as absolutely accurate values, but as relatively consistent across lights in my testing).

SC33 on Hi:

The key measures above are the colour temperature of ~5725K, and a negligible positive tint shift (+0.0103 Duv) to a very slight greenish-yellow at this temperature. For CRI (Ra), I measured a combined score of 58.

These values are consistent with the performance of a cool white XHP50.2 emitter, and match my visual experience of this light. Note that there is a tint shift to more yellowish spill, with purplish spillbeam edge, as is common on XHP50.2 HD emitters.


All outdoor beamshots are taken on my Canon PowerShot S5 IS at f/2.7, 0.5 secs exposure, ISO 400, daylight white balance. The bend in the road is approximately 40 meters (~45 yards) from the camera. Learn more about my outdoor beamshots here (scroll down for the floody light position used in this review).

Click on any thumbnail image below to open a full size image in a new window. You can then easily compare beams by switching between tabs.

As you can see above, the SC33 has a similar tint and overall output to the TS22, although with a different profile – the SC33 is more throwy, and the bezel provides for a less sharp demarcation of the spillbeam edge.

Testing Results

My summary tables are generally reported in a manner consistent with the ANSI FL-1 standard for flashlight testing. In addition to the links above, please see my output measures page for more background.

All my output numbers are based on my home-made lightbox setup. As explained on that methodology page, I have devised a method for converting my lightbox relative output values to estimated lumens. Note that my lightbox calibration runs higher than most hobbyists today, but I’ve kept it to remain consistent with my earlier reviews (when the base calibration standard was first established). On average though, I find my lumen estimates are ~20% higher than most other modern reviewers.

My Peak Intensity/Beam Distance are directly measured with a NIST-certified Extech EA31 lightmeter.

SC33 Testing Results

ModeSpec LumensEstimated Lumens @0secEstimated Lumens @30 secsBeam Intensity @0secBeam Intensity @30secsBeam Distance @30secsPWM/Strobe FreqNoise FreqCharging Current <3VCharging Current >3VParasitic DrainWeight w/o BatteryWeight with BatteryCCT (K)DuvCRI
Moonlight108.88.8---NoNo0.32 A1.50 AYes (not measured)12 g189 g---
Eco504747---NoNo0.32 A1.50 AYes (not measured)12 g189 g---
Low300310310---NoNo0.32 A1.50 AYes (not measured)12 g189 g---
Med750710710---NoNo0.32 A1.50 AYes (not measured)12 g189 g---
High1,8001,8001,800---NoNo0.32 A1.50 AYes (not measured)12 g189 g4,6500.005482
Turbo5,2005,2003,90018,000 cd10,000 cd200 mNoNo0.32 A1.50 AYes (not measured)12 g189 g---
Strobe5,200-----8-14 HzNo0.32 A1.50 AYes (not measured)12 g189 g---
SOS-------No0.32 A1.50 AYes (not measured)12 g189 g---
Beacon------0.5 HzNo0.32 A1.50 AYes (not measured)12 g189 g---

The SC33 seems to match fairly closely to the specs on most levels (although keep in mind that my lightbox’s relative calibration is generously high). Turbo is clearly over-stated however, as it only approaches that output on initial activation – and quickly declines by the ANSI FL-1 standard of 30 secs post-activation.

My NIST-calibrated luxmeter is accurately calibrated to an absolute standard, and similarly reports much lower beam intensity on Turbo compared to the specs. But I find these throw measures reasonable for this kind of emitter and output level.

Note that “Moonlight” is a misnomer here, as >8 lumens qualifies as a low in my view.

To view and download full testing results for all modern lights in my testing, check out my Database page.


As always, my runtimes are done under a small cooling fan, for safety and consistency. To learn more about how to interpret runtime graphs, see my runtimes methodology page. Note that on average, my lightbox’s calibration seems to be ~20% higher than most modern reviewers.




Performance is right where you would expect for a XHP70.3 emitter coupled with a good current-controlled, fully voltage-regulated, high-efficiency circuit. 🙂

It is very much inline with the Wurkkos TS22, but also the various Acebeam and Cyansky lights above. The only real difference is in the actual output levels (both initial and step-down) for each mode. Overall efficiency seems pretty consistent across all these well-regulated models.

Since I know many are interested in how the initial Turbo modes compare (i.e., how quickly and how far the lights step-down), here is a blow-up of the first few mins of runtime on max output:

The SC33 steps down sooner than the Wurkkos and the Acebeam lights, but to a higher stabilized level. As always, it’s your call which pattern you prefer.

Pros and Cons

Light has excellent output/runtime efficiency.Max output is lower than the specs would indicate (although the rest of the output levels seem fairly accurate).
Circuit shows excellent flat-stabilized regulation, with thermally-mediated stepdowns.Light lacks a true moonlight mode.
Solid and sturdy build, with securely attached pocket clipThere are some minor tint shifts across the beam periphery (common on this emitter class).
User interface is fairly sophisticated, and reasonable for the class.
Due to the charging port location and design, physical lockout is not possible, only electronic lockout.
Auto-lockout mode can be disabled.Light is larger and heavier than most in this compact 21700 class.

Overall Rating

Preliminary Conclusions

The SC33 is another strong showing in the high-output 1×21700 class of lights. I would have no issue recommending this light along with the similarly performing Wurkkos TS22, Acebeam E70 and P17, and Cyanski P25. It really comes down to the specifics on the user interface, output level spacing, and build.

There are a number of issues that resulted in losing a full star in my subjective rating system. One of the most significant is the tailcap location of the charging dock, which has required a dual-wall body tube design that significantly raises the size and weight of the light, and prevents physical lockout. While the electronic lockout is serviceable (and the auto-lockout can be easily disengaged), I still prefer a physical lockout on my lights.

The extra bulk and weight is a two-edge sword as well. This may be what allows it to run at higher step-down output level than some of the competition (i.e., extra heat-sinking mass). And some may prefer a heftier light like this. Personally though, I like a more compact light for easier pocketability and carry. I also typically prefer a bi-directional clip (the extra size here reduces the value of a reverse carry option).

Accuracy to published specs is not bad, but not quite as close as some of the competition. I wouldn’t let that hold you back, but I do encourage you to compare the actual performance of lights across my reviews. For example, if maximizing throw is important to you, you may want to look at one of the larger lights with bigger reflectors. More significantly to me, the light lacks a a true moonlight mode, which is disappointing (but may not matter as much to you in a larger light like this).

At the end of the day, I find this to be another quality light from Sofirn. It has a very serviceable user interface, and excellent performance. The price is also very good, especially for the battery-included bundle. As always, it comes down to the specific feature set and build you prefer.


The SC33 was supplied by Sofirn for review. As always, all opinions are my own and the light received the same rigourous and objective testing as all other lights that I have reviewed. At the time of review, this light retails for ~$40 USD (~$55 CDN) on sale on the Sofirn website here.

Leave a Reply

Your email address will not be published. Required fields are marked *