In addition to the SD06 I already reviewed, I was also provided with the smaller SD03 by Sofirn. Visually very similar to the SD06, it uses an 18650 battery and is smaller and equipped with a different LED.
This lamp was sent to me free of charge by Sofirn. I had no influence or other obligations apart from writing a review.
The Sofirn SD03 shown here has not yet been officially launched and is still in development, although some pre-production samples were already sold by smaller shops located in the south-east-Asia area. It is a compact dive light with a single SFT-40 LED, a classic SMO reflector and a magnetic switch with integrated simple lockout, the same as for the SD06.
Please keep this in mind while reading this review. It is likely that some things will be changed for the final sample.
Accessories
The lamp was sent to me in a simple brown box. This is marked with a sticker for the LED type and other information. There is no real difference to the SD06.
It contained a charger and USB-C cable. The charger has 0.75 A charging current, the supplied battery fits perfectly. The case of the charger is very sturdy and should resist common use quite well.
The charger consists of just a single PCB with only a few components on them. The microchip is a CL4056A charging IC.
Appearance, workmanship and feel
Like the SD06, the SD03 is kept very simple in overall design. The rather solid head has large cooling fins and the battery tube has individual recesses to ensure a better grip. This means that the lamp lies securely in the hand even when wet. Due to the smaller battery (18650) the light looks a little bit different in it’s proportions.
The wall thickness of the battery tube could be a little thicker. The curbs in the tube make it appear less solid.
The design is reminiscent of some older Fenix lamps (especially the Fenix PD40 1st gen), especially on the lamp head, and looks great in my opinion. Simple and functional, also like the SD06. The smaller size fits well with its proportions.
The most striking feature is the protruding switch. Unlike most other lamps, this works magnetically: a Hall sensor is actuated by a magnet in the switch, which means that there are no holes in the housing and tightness is ensured. The high button enables another feature: the lamp can be put into lockout mode by turning it. This can also be done with one hand and works both when switched off and on, at any light level, and is a good idea to offer a simple lockout without multiple clicks or similar.
The protruding switch makes it easy to operate even when wearing gloves. The only disadvantage for some users could be the lack of a pressure point due to the magnetic actuation; as with some keyboard switches, the button can be pressed as far as it will go without there being a noticeable click. Since the light is smaller in size, it could be more difficult to handle it while wearing thick gloves. In my test with normal winter gloves it was no problem though.
The most important feature of a diving lamp is its water resistance. The lamp withstood all tests under water jets and submersion at depths of up to 1 m without any problems. Since I’m not a diver, I don’t have any other testing options available to me; however, like an Armytek Dobermann, it has two O-rings on the bezel and battery tube, which should ensure a diving depth of at least 50 meters.
Although the O-rings have been greased, the thread should be re-greased before a dive. There was slightly more grease on the O-rings and threads as with the SD06.
The SD03 is not easy to disassemble. The driver and head are glued.
UI
For UI, there is basically no difference to the SD06, and also the problems with this UI are the same. Three light levels are available.
- Short click of OFF: Start in the last light level (mode memory)
- Long click of OFF: No reaction
- Short click on ON: Switch through the light levels
- Long click on ON: Switch off lamp
- Turning the button to the right: Lockout (also possible when the lamp is switched on)
- Turn the button to the left: Cancel lockout
There are no flashing modes and no hidden menus. There is mode memory in all light levels, so the last mode used is saved and called up when the light is switched on again.
Unfortunately also this model lacks a real low lumens-mode, which is even more important for this type with smaller battery, to get really long runtimes. I would have also two suggestions for improvement here:
A proper low mode (3-5 lm) should definitely be provided, which can be accessed via the unassigned “Long press OFF” function. This ensures that such a mode is not in the normal switching sequence, but can be reached safely and without previous glare by briefly switching off and then pressing and holding. This can be helpful if you need light at close range after a dive on a less well-lit deck, because at the current lowest level, the lamp is far too bright at close range due to its rather concentrated light beam.
In addition, the current lowest light level of 260 lm should be reduced to around 170-200 lm (or even less) to ensure a greater difference to the higher light level, especially when the battery is half empty. I would consider something like this in terms of mode spacing:
- 1500 lm (high)
- 800 lm (mid)
- 150 lm (low)
- 3 lm (moon)
With this adjustment, the lamp would also be suitable for everyday use outside of diving.
One thing which also should be fixed is the slow response speed of the switch. It takes quite some time to switch through the modes due to delay after clicking.
Batteries
A 18650 with Sofirn branding is supplied. It is specified with 3000 mAh. The discharge test with the Vapcell S4+ V2 at 1 A shows 3060 mAh as result, which is good.
If necessary, also other 18650s can also be used. Because of the springs on every side used, even 74 mm long cells fit without problems.
LED
A neutral white Luminus SFT-40 LED with 70 CRI is used. This 3 V class LED does not have a dome and normally provides a good beam, even when using smooth (SMO) reflectors. The SD03 is equipped with just that.
Unlike most Luminus emitters, this LED in my sample tested has a good tint, even at low current. Unfortunately there is very heavy tint-shift in the higher modes, the tint changes extremely to more cool white with slightly negative duv. Since I was not able to test a 5000 K SFT-40 yet, I cannot say for sure this is due to the LED itself or just high thermal resistance (bad reflow or something).
The front glass has an apparently high material thickness (2-3 mm), but is not AR coated. I recommend a proper AR coating, since other Sofirn lights have these.
Running times
Running time test in cold water (immersion conditions)
Used luxmeter: Benetech GM1020 in data-logging mode
The runtime diagram raises more questions than it answers. The curve is atypical for a well-regulated lamp, especially under cooling (immersion conditions).
After an initial stepdown to around 1200 lumens, there is another hard stepdown to around 600 lumens after around 8 minutes. Instead of ensuring a constant brightness here, the brightness continues to increase over the course of around a quarter of an hour before dropping back to the original value over the following 20 minutes.
Something doesn’t seem to be right here, like the temperature control is trying to maintain the previous brightness level despite the previous stepdown, which makes little sense in view of the other regulation behavior.
Towards the end, the lamp starts to flash to indicate an empty battery. The lamp then switches off, but can still be switched on briefly at the lowest level.
Runtime uncooled
If there is no cooling, the regulation is as expected: Stepdown to the next lower level. Only a brief switch-off before the step-down to the lowest level (at around 100 minutes) is noticeable here.
Performance
The lamp heats up fairly quickly on the highest setting. It reduces the maximum luminous flux before the surface temperature becomes too high. The temperature does not exceed 53 to 55 °C.
The heat distribution is not evenly (shown after around 2 min operating time). Only the head heats up. The battery tube cannot really contribute to heat dissipation, which is different to the SD06 where all of the light is heated up more evenly.
The following measured values were taken with the supplied 18650 @ 4.18 V (Charger: Vapcell S4+ 1000 mA charging current):
An integrating sphere was used for following measurements, luxmeter: Voltcraft MS200-LED.
| Mode | Light flux | Brightness |
|---|---|---|
| Turbo (battery full) @ 5 sec | 1505 lm | 42500 lx |
| Turbo (battery full) @ 30 sec | 1451 lm | 41200 lx |
| Mid @ 5 sec | 897 lm | 25300 lx |
| Mid @ 30 sec | 891 lm | 25100 lx |
| Low @ 5 sec | 339 lm | 9570 lx |
| Low @ 30 sec | 338 lm | 9560 lx |
Beam quality
The beam is very good. There are no color distortions in the spill or around the spot; rings are only visible on the whitewall if you look closely.
The SD03 is more like a pocket thrower. Without having a real low light level, using the SD03 in closest range is almost impossible without getting dazzled. In this regard adding a fourth mode with 3-5 lumens is strongly recommended.
The tint shift is clearly visible and somewhat annoying, even in nature.
Conclusion
Like the SD06, the SD03 is actually aimed at divers. In general, both models are very similar apart from the LED and battery. And so the problems of the SD06 are similarly applicable to the SD03.
However, like the SD06, the SD03 is just as good a no-nonsense lamp, which can also be used by people with little affinity for flashlights without having to access hidden menus or certain operating modes.
Thanks to the 5000 K LED, this lamp is in principle also suitable for (underwater) photography, although the low color rendering value could pose a problem here.
Pro
- Simple design without frills
- Battery and charger included
- Switch with very simple lockout
- very simple UI
- no flashing modes (strobe etc.)
- fully waterproof
- good beam without annoying artifacts
Cons
- lowest light level much too bright, therefore hardly or not at all usable at close range
- very big tint-shift in higher modes (towards cool white)
- weird regulation especially in cooled operating conditions
- no AR coated glass
Hope this review is useful for you! 
Best regards, Dominik