[Review + color/runtime testing] Convoy S21F – A real Hi(CRI)-light?

Review EN

Convoy S21F – A real Hi(CRI)-light?


To be honest, reviews of flashlights were never a real thing for me on BLF. In the last years I also neglected my LED testing, and other things were more important in my life as LEDs or lighting technology. Nowadays I am more able to get into the topic again, and to write some reviews of lights I really like. This is one of my first lights I bought after around six years.

Despite my skepticism of the advancement of flashlights, the leap was quite noticeable when I held new lamps in my hand, and among them was the S21F.

This one caught my eye more by accident while browsing on Aliexpress, as a lamp that looked very promising with dual channel tintramping and the internal charging function, while also offering a very attractive price. I purchased two of these lamps on a regular basis.

Note: both lamps in this review are my own S21F. The LEDs on the brown version are dedomed to use a lower color temperature primarily for residential lighting. This will be discussed separately later. The scratches and quirks on the brown S21F are due to months of use and constant transport in bags, toolboxes and the car.

First impressions

The S21F was delivered together with an already attached lanyard in an simple white cardboard box. There were no instructions or other accessories like replacement O-rings or a holster inside.

The S21F has a quality feel to it, helped by the solid wall thicknesses. The black anodizing feels some kind of ‘smooth’, almost like the finish of the Armytek lamps. The threads are cleanly worked, although these were almost not greased at all. So here is especially important to lubricate the O-rings, because they were completely dry!

The Quad lens is protected by a coated front glass. Under the stainless steel bezel is an O-ring, which ensures the tightness to the lamp head.

Due to be slightly tail-heavy, it lies very well in the hand. All in all, the quality is as good as it is known from Convoy.


Due to the smooth end cap, the S21F can be used in tailstand without restrictions, even with a lanyard attached.

The side switch can be found blindly, although there could be some confusion due to the rear charging port cover which feels almost the same as the switch. With gloves, this is significantly more difficult, whereby in such a case, a lamp with a rear switch should always be clearly at an advantage.

The lamp only has limited rollaway protection. On slight inclines, the lamp stays put, but then it rolls away.

There are LEDs in the side switch, which indicate the battery status with green and red. When the battery voltage is low or the charging process is taking place, the side switch lights up red, otherwise green. The S21F does not have a function for permanent illumination of the side switch (Aux LEDs).

The lamp offers internal charging. The USB-C port is closed with a rubber cap, which held flawlessly tight for a continuous hour at 40 cm water depth with my lamps. Almost all USB-C cables fit into it.

Even with use of a Anker powerbank the battery is charged with 1.9 A, while the manufacturer specifies 2 A. The battery voltage after completion of the charging process is 4.18 V.

The lamp is not glued. It can be completely disassembled:

It will fit longer protected batteries. I use the Fenix ARB-L21-5000 in the S21F, which is primarily for residential lighting. Thanks to the springs on both sides, it fits without being compressed. With the mentioned Fenix battery is also Turbo (according to the manufacturer 8 A) usable without any problems.

User Interface (UI)

This lamp has a simpler UI. Generally, this topic is discussed quite emotionally in the meantime, whereby the user’s preference has absolute priority here. Thus, my opinion on the UI is not universally valid.

Like the other Convoy lamps, the S21F does not offer Anduril or other operating concepts. Personally, I very much welcome the decision, as it is precisely the UI of Anduril (2) that puts me off Emisar’s undoubtedly very high-quality dual-channel lamps.

UI description:

  • When OFF, short click → lamp turns on to last brightness (mode memory).
  • 1x click and hold: brightness increases → release to stop ramping
  • if OFF, long click and release → Moonlight
  • if OFF or ON, double click → Turbo
  • If ON, 1x click and hold: Color temperature adjustment (tint ramping) → release to stop ramping
  • If OFF or ON, click 3x → Strobe, double click → SOS, click 1x → OFF
  • If OFF, 4x click → tactical mode (Momentary light 100%), 4x click very fast to exit, or twist endcap open once and close again
  • When OFF, click 5x → battery status display, in 1 or 0.1 volt steps. Example 3.7 V: *** pause *******, click 1x to exit
  • If OFF, click 6x → change from ramping to 4 light levels (1%-10%-40%-100%), click 6x to cancel. ATTENTION: This mode is saved after battery change!
  • When OFF, click 10x → Lockout. Click 10x to cancel. ATTENTION: This mode will be saved after battery change!

Interesting discovery: after unlocking the lockout, the LED of the side switch lights up permanently, green or red depending on the battery status. However, the “Aux LED” thus created is turned off again after one use.

For those who want a lot of setting options or modes, the S21F is nothing. It limits itself to the essentials: Adjust CCT and set brightness. It is this simplicity that makes it for me a lamp that can also be operated “quickly times” in a hectic, without giving up the CCT setting. After a short period of getting used to it, operating errors do not occur at all.

The “Moonlight” is unfortunately much too bright, especially for going to the toilet at night. Why this is so bright is not really clear to me from a technical point of view, since the driver can deliver a much lower current per channel as can be observed when tint-ramping.

The ramping takes a relatively long time and a difference is hardly noticeable, especially in higher brightness, which means that it is sometimes not immediately obvious in which direction the driver is ramping.


As of today, the Convoy S21F is exclusively available with Nichia 519A LEDs in R9080 (Ra typ. 90 - R9 min. 80). These are also installed without any doubt, on the left the dedomated LEDs of my second S21F.

Two LEDs each in CCT 2700 and 5700 K are installed, recognizable by the different yellow coloration of the phosphor.

Whether NVSW519 or the newer NVSW519-V1 are installed is unclear, though. The -V1 variant (on sale since May 2022) is characterized in particular by a lower Vf and slightly higher efficiency bins, although the light color could possibly suffer here, as a higher green part in the spectrum is usually added for increased efficiency.

Dedoming is very simple. The dome can be easily lifted off with a fingernail, and the phosphor is protected from damage by a glassy layer. The easiest way to do this is when the lamp is warm, e.g. when it has been running on turbo for a short time. Any residue left around the luminous surface does not affect the light quality.

Light and light image

The light is just awesome!

At 5700 K, the tint is a clear snow-white, without any color distortions. The color rendering is already impressively good without using measuring equipment and can be seen easily by naked eye. I was immediately reminded of the 219BT-V1, which was the benchmark for light quality a few years ago.

At 2700 K, there is a pure warm white, which is otherwise only known from very good living room lighting. Due to the lens with a very wide beam angle, the light is well mixed, there are no disturbing color fringes or different coloring in the beam! This is also true for the variant with dedomed LEDs. Here, dedoming primarily changes the color temperature and the light color. The beam angle is only insignificantly affected, the S21F is also in dedomed state a pure floodlight, even if the brightness in 1 m measurably increases.

The color rendering is impressive and in the top range. In the original state, the deviation from the blackbody curve (duv) is almost perfect when using only one of the two CCTs (channels); in mixed mode, this transforms into a beautiful, minimally reddish and thus subjectively extremely pleasant light, which is also clearly visible in the color spaces above. Coupled with the original optics used, this makes for a lamp that can easily be used indoors as ambient or mood lighting.

(left dedomed, right original)

For the S21F with dedomed LEDs, this applies to an even greater extent; due to the significant deviation, a distinct red coloration (compared to other emitters) occurs in mixed operation, although this is not disturbing and even turns into an advantage, especially in nature. The color rendering hardly suffers from the dedoming, the Ra decreases here by 2-3.

There are alternative optics with other beam angles available to significantly influence the light pattern. However, these are not currently available to me.


One thing up front, this is the first lamp where I didn’t feel the need to even know the performance or otherwise improve the performance. For me, it was just perfect the way it was, and with how fun it was to use, I didn’t see the need to mod anything else except for Dedoming after some time of use…

The measurements are just for the completeness of the review.

Battery and Measurements:

Samsung INR21700-40T @ 4.18 V (charged in Vapcell S4 Plus @ 1500 mA).

Integrating sphere IS-108

Luxmeter: Voltcraft MS-200LED

22.2 degrees @ 41 % rh

Luminous fluxes

  • Original Turbo: 1889 lm

  • Original 100% 2700K: 950 lm

  • Original 100% 5700K: 1341 lm

  • Dedomed Turbo: 1623 lm

  • Dedomed 100% 2700K: 788 lm

  • Dedomed 100% 5700K: 1134 lm

  • Moonlight (original): 9,9 lm

Brightness @ 1m

  • Original Turbo: 2950 lx

  • Original 100% 2700K (cw): 1510 lx

  • Original 100% 5700 K (ww): 2070 lx

  • Dedomed Turbo: 3780 lx

  • Dedomed 100% 2700K (ww): 1860 lx

  • Dedomed 100% 5700K (cw): 2590 lx

The S21F is temperature controlled. Normal handling does not become painful with it. Interestingly, after reaching the maximum of about 50 degrees, the temperature at the lamp head drops again, to about 44-46 degrees. This is achieved by a significant reduction in luminous flux.

The thermal images were taken in the period of about 4 minutes, with the lamp (original LEDs) on Turbo. In general, it can be said that it gets warm very quickly, especially on Turbo, this becomes noticeable after a few seconds when the lamp is completely cooled down.

The S21F has a buck driver with integrated charging circuit, which can provide a constant current until the LED Vf is reached. In the runtime diagram shown below, the lamp was cooled as best as possible to represent the absolute ideal case.

The driver holds the maximum luminous flux for a relatively long time, then drops a bit to hold the current until Vf is reached. Only then does the driver switch to classic linear control. (With turbo, of course, this happens much faster than with a low light level). When a too low (load) voltage is reached, the side switch lights up red and the lamp starts flashing about every 30 sec, which is clearly visible in the diagram.

When the voltage is too low (about 2.8-2.9 V), the lamp finally switches off. It can be turned on again after that, at lower luminous flux, where it drops extremely fast and it turns off again quickly, as seen in the diagram. A solid approach nonetheless, as you are not simply left in the dark, but have some remaining operating time.

Unattractive: when removing the LED board, I noticed the following…

Was now in operation no problem, because the heat transfer was absolutely given, but the burrs on the LED board could massively worsen the heat transfer from board to host. By applying plenty of thermal paste, this problem was not relevant in everyday use, although the long-term durability (drying out of the thermal paste) then plays a particularly important role…


Here are some beamshots from my last vacation. In this Lost Place the flooded light image is clearly visible, although there is no throw visible.

For someone who needs light at close range, this is absolutely usable. This light is also good for photography, especially since there is no PWM even on lower brightness settings.


Is the headline exaggerated? Yes and No. Yes because there are of course similar lamps with a similar concept and also extremely good light quality. No but also because it becomes one of my lights most used, because I just need light almost only in the near vicinity.

It’s relatively compact, offers good battery life thanks to the 21700, and provides good constant current control thanks to the buck driver, and I really like the simple UI without many settings or special hidden modes.

Considering the price of about 35 € incl. shipping to D an absolutely recommendable lamp, if a flooded light image is important. For about 5 € you can order 4 lenses to change the light image.


  • very good price-performance ratio
  • impressive light quality
  • tint ramping
  • USB-C charging with 2 A
  • very good control incl. temperature monitoring


  • simple UI without many setting options
  • no aux LED
  • extremely fluid light pattern


  • much too bright moonlight
  • switch not very good tactile
  • slow ramping speed
  • burrs on bottom side of LED board (-> possibly long term heat problems)

I hope you enjoyed the review! :slightly_smiling_face:

Many greetings, Dominik

4 Thanks

Thank you…this is an excellent review and I am enjoying my S21F! I’ve been trying out the different lenses just today and have settled on the 30 degree beaded, as it’s a good compromise between 60 and 10 (which is what came in the pack from Convoy AE store and the 60 the unit shipped with originally).

Slightly off topic, but are those tank traps in one of your photos btw? May I ask what country you are in? The area I grew up in the UK had a lot of tank traps and pillboxes so it was interesting to see, especially illuminated like that.