REVIEW: Sofirn C8F 21700 (comparison, beamshots, teardown PIC HEAVY)[21700, 3x XP-L HD, C8 format]

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Skylight
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REVIEW: Sofirn C8F 21700 (comparison, beamshots, teardown PIC HEAVY)[21700, 3x XP-L HD, C8 format]

This is my review of the Sofirn C8F 21700. The flashlight has been supplied by Sofirn for review. Many thanks to Sofirn!

Introduction

The Sofirn C8F 21700 is a C8-sized flashlight with three XP-L leds in a smooth triple reflector. It uses a 21700 battery but includes a sleeve that allows to use 18650 batteries as well. The Sofirn C8F runs in direct drive and has several mode groups, one of which is ramping. It is the successor of the Sofirn C8F which used only 18650 batteries, had no tail switch and a sligthly different design. The Sofirn C8F 21700 is a well made upgrade with longer runtimes and (maybe) brighter turbo due to the 21700 battery.

Purchase links (non affiliate)

Amazon IT: https://www.amazon.it/Sofirn-potente-Luminosa-3500-Lumen-leggero/dp/B07G...

Amazon DE: https://www.amazon.de/Sofirn-Leistungsstarke-Taschenlampe-Lichtgruppen-L...

Amazon US: https://www.amazon.com/Tactical-Flashlight-Battery-Charger-Camping/dp/B0...

Aliexpress: https://www.aliexpress.com/item/32914324213.html
Link for the host: https://www.aliexpress.com/item/32915961393.html
Link for the bag (medium size): https://www.aliexpress.com/item/32972983004.html

Banggood: https://www.banggood.com/Sofirn-C8F-21700

First impressions

The Sofirn C8F 21700 follows the usual high standard of the Sofirn flashlights with square cut threads, AR-coated glass lens and nice black anodizing. Actually, this is not my first experience with this flashlight as I already own the host version from the Sofirn store on Aliexpress. So I know already that the build quality of the host is impressing as well as the aestetically appealing design and form factor. This way I got the opportunity to compare the stock version of the Sofirn C8F with my build using XPL2 leds and a NarsilM TA driver. I will show you the results in the comparison part of my review.

Here you can see the plain brown Sofirn cardbox with the C8F inside:

What is included

- Sofirn C8F 21700
- lanyard
- 21700 Sofirn battery 4000mAh
- two spare o-rings
- adapter sleeve for 18650 batteries
- single slot battery charger
- Micro USB cable
- manual

Specifications

These are mostly the specifications claimed by Sofirn (weight are my data). I did not test the lumen, throw or waterproofness but they seem to be reasonable.

- Led: 3x CREE XPL HD V6
- 3500 lumen, 299m
- AR coated glass lens
- Smooth triple reflector
- Battery: 21700 or 18650
- Dimensions: 149mm(length), 44.6mm(head diameter)
- Weight empty: 192g
- Weight with battery: 260g
- IPX8 Water resistant, underwater 2 meters for 30 minutes
- Low Voltage Protection
- Reverse polarity protection
- Advanced temperature regulation (ATR 50°C)

Dimensions

Length: 148,6mm
Head diameter: 44,6mm
Head height: 66,0mm
Battery tube length: 72,3mm
Battery tube ID: 21,86mm
Battery tube OD: 27,4mm
Diameter at threads: 25,7mm
Tailcap diameter: 30,6mm
Tailcap height:31,0mm
Reflector height: 19,86mm
Reflector diameter: 39,46mm
Single reflector ID: 19,20mm
PCB diameter: 29,95mm
PCB thickness: 1,55mm
Distance led pad to center: 8,63mm
Switch PCB: 22,96mm
Switch retaining ring: 23,79mm
Spring wire diameter tail: 0,72mm
Spring wire diameter head: 0,73mm
21700 battery diameter: 21,70mm
21700 battery length: 70,80mm

User interface

The Sofirn C8F is switched on or off with the forward clicky tail switch while the modes are changed with the momentary side switch. You can either turn off the flashlight with the tail switch or lock it out by unscrewing the tailcap with anodized threads. The side switch is lighted and works as a battery indicator. The leds are green as long as the voltage of the battery is sufficient and switch to red if voltage is low.
On the C8F you can choose between four mode groups by clicking the side switch four times. Group 1, 2, and 3 have one, three and four modes. Group 4 is stepless ramping from moonlight to Turbo. The moonlight is accessed with a long click from off whereas the turbo requires two short clicks. In the stepped modes, high is not turbo, even with four modes the turbo is hidden and you need to click twice for maximum output. When you click four times for changing groups the flashlight will give two short blinks to confirm the choice. By default, the C8F is set to four modes, the next group is ramping. If you want four modes again you need to click for a total of twelve times with the blinks in between to get group 3 again. Make sure your clicks are fast and consecutive otherwise the flashlight won’t react.

The Sofirn C8F in action with the green switch leds

Leds on moonlight

Appearance

Front view

Rear view

Different side perspectives


The three parts of the flashlight: head, battery tube and tailcap

This is the battery cover that gives additional security during shipping and needs to be removed before using the flashlight for the first time.

Detail of the driver with the factory bypassed spring

The tailcap, housing the forward clicky switch with bypassed spring

Close look at the deep, square cut and anodized threads

At Sofirn’s Aliexpress store you can purchase a bag for the flashlight. It fits the Sofirn C8F perfectly and I really recommend you the holster if you plan to transport your C8F a lot.

Battery and charger

The battery is a 21700 with Sofirn wrapper. I measured 37 – 47 mOhm internal resistance with my Miboxer charger. This is the value which also my Liitokaala 26650 typically show, so the cell should be capable of 15–20 A output. Along with the 4000mAh capacity this is a nice rating for a 21700 battery and offers a good capacity to output ratio.

The charger is a single slot charger with a slider long enough to fit also 21700 batteries. It charges at 0.75A so it should take around five hours to get the battery fully charged. The charging rate is a bit less than 0.2C and will guarantee a long battery life.

The battery inside the charger

The Sofirn 18650 3000mAh and the Sofirn 21700 4000mAh

Comparison of the 21700 and the 18650 Sofirn battery in the adapter

Left is the 21700 battery inside the battery tube, right is the 18650 battery in the tube

Comparison pictures

Big Sofirn lights (from left to right): 18650 Sofirn battery, 21700 Sofirn battery, Sofirn SP31 V2.0, Sofirn C8F, BLF Q8

Small Sofirn lights (from left to right): , Sofirn C01S, Sofirn SP10S, Sofirn C8F 21700

Some well known flashlights (from left to right): 21700 Sofirn battery, Emisar D4, Convoy S2+, Convoy C8+, Sofirn C8F

Comparison of the stock C8F with my XPL2 host build

From left to right: 21700 battery, Sofirn C8F host, Sofirn C8F stock version (note the absence of all white brandings on the host version)

Left 4000K XP-L2 V6, right 5200K XP-L V6

Both flashlights on moonlight

Whitewall shot on turbo. The stock Sofirn C8F has a much cleaner beam with less yellow and tint shift. The tint shift is much more noticeable on my XPL2 C8F, although it is not that disturbing with 4000K. The tint shift would look ugly with 5000K XPL2‘s cold white hotspot and yellow corona, that may be the main reason why the Sofirn C8F doesn’t use XPL2 leds.

Beamshots

Whitewall beam comparison of the Sofirn C8F, BLF Q8 and the Sofirn SP31 V2.0. You can clearly see that the SP31 is the coldest (around 5300K), the C8F is slightly warmer (maybe 5200K) and the BLF Q8 is around 4900K. All flashlights on turbo, about 30cm from the wall, the white balance is set to 5000K.

Whitewall beam comparison: Sofirn C8F, Emisar D4 XPG2, Emisar D4S 219C

Tint comparison on a white wall: left Convoy S2+ triple with 4000K SST20 FD2, middle Sofirn C8F 5100-5200K XPL, left Fireflies E07 with 6500K SST20; The color temperature increases from left to right, while the rosiness decreases.

Outdoor beamshot of the Sofirn C8F on Turbo (3.2s, F7.1, ISO400)

Control shot without flashlights (same settings)

Comparison of the Sofirn SP31 (left) and the Sofirn C8F (right)

Comparison with the BLF Q8 (left)

Comparison with the Emisar D4S 219C (left)

Teardown and internals

Here is a quick teardown with some pictures of the internals. I suggest you not to try a teardown unless you know what you are doing and want to mod something. For detailed measurements see ‚Dimensions‘.

The driver with the switch and the screw that holds the reflector

Other side of the driver with the MCU, the main wires are 24AWG.

When the reflector screw is loose you can pull out reflector and MCPCB. The amount of thermal paste is sufficient, maybe that white paste is not the best, the grey one is normally better.

Assembled switch as it comes out of the tailcap

The big forward clicky switch with 14mm button

Front of the 23mm switch PCB

The triple reflector from behind, three holes for the leds, one for the MCPCB screw

The 30mm copper MCPCB with the three XP-L V6

Conclusions

In my opinion the Sofirn C8F 21700 is another well manufactured flashlight from Sofirn. The stock version without any modifications is already good and there is also a host version for people with DIY abilities. I’m astonished how good this flashlight handles the heat of the three XP-Ls, it should be able to run on 1000 lumens until the battery is empty. The ramping is not as linear as NarsilM or Anduril but still good and quite similar. The Sofirn C8F is a perfect allrounder.

What I like

- Deep, square cut threads that screw very smoothly
- High grade black anodising, also on the threads for lockout
- Cooling fins and good knurling on the battery tube
- Ramping is available, similar to NarsilM or Anduril
- Wide scale from very bright turbo to low moonlight
- The host absorbs a lot of heat, it gets hot only after 30s on Turbo
- The C8 form factor is ergonomic and fits bigger bags without being to heavy
- It is not much, if any, bigger than most 18650 flashlights but uses 21700 batteries.

What could be improved

- The two clicks for turbo and the four clicks for changing group need to be very fast without the smallest break. The driver MCU should be set to recognize also slower clicks.
- Maybe it’s only me but I would always opt for a 4000K option.

Many thanks to everyone for reading! If you have any questions or want further information please feel free to ask and comment below.

My 7th Old lumens contest build: Matainvoy ML18S

My reviews: Sofirn SP31 V2.0Nightwatch NI40 StalkerSofirn C8F 21700Brinyte WT01 Apollo

Edited by: Skylight on 11/29/2019 - 05:33
Skylight
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Reserved

My 7th Old lumens contest build: Matainvoy ML18S

My reviews: Sofirn SP31 V2.0Nightwatch NI40 StalkerSofirn C8F 21700Brinyte WT01 Apollo

Rdubya18
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Very nice review thankyou . I really like my C8F . I had accidentally ordered the Utorch C8F at the same time . I found it much brighter than the Sofirn. I contacted Sofirn about it and they never responded , so I pretty much use the Utorch . It’s a good all around light.

Skylight
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The difference in brightness could be caused by a different FET with lower internal resistance. It is also possible that Utorch used 22awg wires instead of the 24awg Sofirn uses.

If you want the maximum brightness you should try to swap your C8F’s driver with one from Lexel. He made a driver just for the Sofirn C8F.

My 7th Old lumens contest build: Matainvoy ML18S

My reviews: Sofirn SP31 V2.0Nightwatch NI40 StalkerSofirn C8F 21700Brinyte WT01 Apollo

AndyMac2272
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Great review. Thank you.

AndyMac222777

Rdubya18
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I’m going to look into that . I was just playing with it because this thread reminded me of that difference in the two lights . My lumen tube was reading around 1500 lumens on the Sofirn. I noticed the bezel wasn’t seated tight , but after tightening it , the light came on and would not respond to the side switch. It was much brighter than previously so I stuck it on the tester and it was reading 3300 lumens. I found the driver retaining ring was somewhat loose so I tightened it . The side switch then worked , but it only read 1200 lumens and no turbo . Loosening the ring slightly returned it to how it was . Didn’t have time to investigate further , but I’m not really sure what it is I’m looking for . Any ideas ? I thought at first a driver issue , but now wonder if it’s a connection problem . I have been wanting to try on on Lexels drivers , maybe the time is now.

Skylight
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AndyMac2272, thank you. Smile

Rdubya18, if the flashlight is very bright and does not respond to the switch the negative wire is touching the reflector or MCPCB and the leds are running directly connected to the battery. You could open the C8F and look if the wires are connected well. When you see the negative wire could touch the reflector put some Kapton tape on the reflector or on the contact point. I had shorting issues as well when I built my C8F host.

It is strange that tightening the retaining ring decreases lumens. Normally it should improve then. The bezel should be screwed tight as well. The C8F has a screw to hold down the reflector and one screw to connect MCPCB and reflector. So these screws ensure good thermal contact which is crucial for turbo performance. Of course there shouldn’t be any electrical contact.

My 7th Old lumens contest build: Matainvoy ML18S

My reviews: Sofirn SP31 V2.0Nightwatch NI40 StalkerSofirn C8F 21700Brinyte WT01 Apollo

Rdubya18
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Thanks Skylight , the pinched , or shorted wire was my first check . I did noticed the insulation on the negative wire looked flattened in a spot but did not see a nick in it . I just tried to put back together carefully , but maybe should just replace that wire . I did not understand the outcome of the retaining ring either , but perhaps it is related to the ground also. I never thought about taping the reflector . Thanks for pointing out that possibility. While I have done some mods and builds , I’m definitely still learning .

Dioda
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Hey Skylight,

how is the beam profile compared to the BLF Q8? Does the C8F has any decent range? Im considering it for its size format and beam profile that seems like mix of flood and throw.

Skylight
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Dioda, the beam profile of the C8F is quite similar to the BLF Q8. It is indeed a mix of flood and throw. The C8F beam profile is rounder than on the BLF Q8 which is more square formed due to the quad reflector. The hotspot of the Q8 might be slightly bigger with more spill and higher brightness.

The C8F reaches trees 150m away easily. So it is not a dedicated thrower but a high output flashlight with some throw. It gets hot fast on Turbo but not quite as fast as the D4S or E07. I like the form factor too. It fits in the palm of your hand and maybe also in a bag.

My 7th Old lumens contest build: Matainvoy ML18S

My reviews: Sofirn SP31 V2.0Nightwatch NI40 StalkerSofirn C8F 21700Brinyte WT01 Apollo

Dioda
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Hey Skylight, many thanks for your useful detailed info. The C8F interests me mainly due to rare combination of good price, decent output and beam profile that suits my needs around the cabin or while in the woods and acceptable UI. The Q8 works very well for these tasks as well, but it is too heavy to be thrown into pocket when needed. By the way, how similar is the tint to the tint of Q8? According to review videos it seems that it is also quite neutral, not the cool bluish white.

Skylight
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I’m glad if I can help.

The tint of the C8F is not much different from the BLF Q8. Personally I prefer the slightly warmer and more yellow tint of the Q8 but you will notice the difference only if you use them together. You can have a look at the whitewall beamshots in my review. The Sofirn C8F has neither too much green nor blue in the beam and the color temperature should be between 5000K and 5200K.

I never used the C8F outdoors but I would expect it to be a useful light for night walks. The hotspot is not too tight and bright but it allows you to see your way without having to turn up the brightness too high. The 21700 provides good runtime and the turbo can be reached fast with a double click. It is hard to beat for that price.

My 7th Old lumens contest build: Matainvoy ML18S

My reviews: Sofirn SP31 V2.0Nightwatch NI40 StalkerSofirn C8F 21700Brinyte WT01 Apollo