Review: Runcam Split 4 Camera – Making the World’s Smallest 4K FPV Drone

by Oscar

The Runcam Split 4 is an HD camera capable of recording 4K videos, designed to be mounted in tiny whoops or “toothpick” micro drones. I managed to install it in a 65mm whoop, possibly the smallest 4K FPV drone.

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The World’s First 4K 65mm Tiny Whoop

I simply replaced the BetaFPV Nano HD camera in the Beta65X HD with the Runcam Split 4. This tiny 65mm FPV drone can now record 4K videos! :)

It was easy to swap out the camera, as they both have similar size, except the lens module. I had to drill a couple of holes in the canopy to mount the lens.

I also had to trim away some plastic in the canopy to access the buttons. Still need to add protection to the lens, maybe some foam or a lens cap.

The weight without LiPo is only 34g, 2.5g heavier than before. This is a 2S whoop, so the extra weight should be manageable.

I am sure you can do the same upgrade easily on other micro drones too :)

Where to Buy Runcam Split 4

It comes with a “nano to micro” adapter (14mm to 19mm width), some M2 screws, standoffs and nuts, and a 3-pin JST cable for connecting to your FC.

Specs and Features of Split 4 Camera

The Runcam Split 4 is an HD camera, but it can be used as an FPV camera at the same time. The averaged latency according to Runcam is 55ms, slightly higher than dedicated FPV cameras, but low enough to be flyable.

It’s one of the smallest / lightest HD cameras that can record 4K videos. With the 25.5×25.5mm mounting holes, it can be mounted on top of “whoop style FC” – many tiny whoops and toothpick builds use this type of FC.

When the camera is powered off by accident (e.g. battery ejected in a crash), it will automatically save the video, so you won’t lose the footage. (it will cut off the last 3-4 seconds, but better than losing the whole video!)

You can control the camera using your switches on the radio (start/stop recording, navigate OSD menu), simply by connecting the camera to the flight controller, and set it up in Betaflight.

The Split 4 camera supports 5V to 20V as input voltage, which means you can power it directly from a 2S, 3S or 4S LiPo if you want, but it’s not recommended as voltage spikes could damage it. It’s best to power it from a BEC.

  • Image Sensor: SONY 13MP
  • Field of View(FOV): 140°
  • Video Resolution: 4K@30fps/2.7K@60fps/2.7K@50fps/1080P@60fps
  • Video File Format: MP4
  • NTSC/PAL Switchable
  • 16:9 and 4:3 aspect ratio switchable for FPV
  • Max Micro SD Card Supported: 128GB (See my SD card recommendation)
  • Wide Input Voltage: 5V to 20V DC
  • Lens Module Size: 14*14mm
  • Mounting Holes: 25.5*25.5mm
  • PCB Size: 29*29mm
  • Working Current: Up to 450mA at 5V (2.25W)
  • Weight: 10.2g

Closer Look at the Split 4

The Split 4 only weighs 10.2g!

Compared to the previous Runcam Split 3 Nano, the lens module sizes are similar, but the Split 4 has a different lens – appears to have wider aperture.

Left: Split 4; Right: Split 3

The PCB is slightly wider in the Split 4.

Top: Split 3; Bottom Split 4

Here are some close up shots of the PCB.

The ribbon wires are very strong and well protected, almost impossible to pull off from the PCB or the lens module. They used the same design/material in the older Split 3 and it’s been proven to work reliably.

The lens module is a 14x14mm nano size camera, with M2 screw holes on both sides.

There are two buttons – Power/Shutter button and Mode button. You can use these buttons to change settings through the OSD menu.

Alternatively, you can also solder your Runcam joystick to this camera, it’s much easier to navigate the menu with it.

They have added shutter speed to the image settings, which is amazing. This is a must have setting if you were to use ND filter and create silky smooth FPV footage, having a fixed shutter speed means your video exposure will be a lot more consistent.

Solder pads are well sized for easy soldering.

I am a little concerned by how far the SD card sticks out. But it doesn’t seem to be an issue though in my Beta65X build, but something to take note of.

Image Quality

See HD and FPV feed image quality in this video, comparing to the Split 3 Nano:

Watch it and decide for yourself, here are some of my own findings:

  • Field of view is wider, especially in FPV mode
  • Colors in FPV feed are much nicer to look at, more natural
  • Saturation in HD is much lower in the new version, possibly better for color grading in post
  • It has less image distortion than the previous Split 3
  • Audio is better
  • Default Sharpness and WDR are similar
  • Bit rate of 4K raw footage is 61Mbps, a 40-second video is about 310MB

And I think I found a problem with FPV feed stuttering when recording in 4K. It doesn’t always happen and seems to be random. Changing PAL/NTSC didn’t fix it. I’ve contacted Runcam about this and see if they can replicate the issue and fix it in a software update. Update: issue fixed in the latest version (1.1.5), hopefully all production units has this firmware (or newer).

Runcam Split 4 Connections

Here are the buttons and pin-out of the Runcam Split 4.

The only important connections are VCC (red), GND (black) and Video (yellow). You don’t have to connect RX and TX, these are for connecting to the FC if you want camera control

Basic Operations

How to operate the Runcam Split 4:

  • To Power on, long press the Power/Shutter button, solid blue LED means the camera is powered on
  • Press the Power/Shutter button to record, and blue LED will begin to blink
  • To access the OSD menu and change camera settings, long press the MODE button (when you are not recording), you will see a solid orange LED
    • Press Power button to move to the next setting
    • Short press MODE button to change setting
    • Long press MODE to exit

How to Setup Camera Control?

You can start/stop recording and navigate through OSD menu using the switches on your radio. Here is how to set it up.

First you have to find a spare UART on your FC, and connect the TX and RX pads.

Enable “Runcam Device” for this UART in the Ports tab in Betaflight.

And assign switches to these modes.

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ztallion 22nd April 2021 - 10:43 am

thanks for the article,
i’m having hard time to find what components/screws should i use to stack it on top of my whoop fc,

if you can give us more details about this part of the build

Oscar 22nd April 2021 - 12:02 pm

Sorry i don’t have this quad anymore, but from memory I think I just used screws that came with the quad and the camera, i don’t think I used any special screws.

Seth 3rd February 2021 - 1:39 pm

But would it work on soft serial with a tx only to get some function? In my setup all I have left is a soft serial tx only from my f411-wse. U-1 is GPS, U-2 is fport frsky r9mx, soft serial 1 is st1 tx pin to vtx, and the last remaining tx is for soft serial 2. My board apparently won’t do rx out of the FC on soft serial and well i only have one soft serial open so its Tx that i have available. Can I gain some recording and setup control with only tx to rx on the split being controlled on a soft serial?

I should add that there is a camera switcher on the board but i’m pretty sure that just changes the power and input on the FC to another set of pads which i don’t think would help me here.

Tony Pass 18th October 2020 - 11:37 pm

Can you purchase a replacement lens for the split 4 nano? I can’t find them any where and hoping I don’t have to buy a new camera and board just to replace the lens.

Marcus 30th August 2021 - 8:18 am

Having the same issue – I don’t see any replacement lenses listed for this – hard to recommend a one and done product. Anyone have any luck finding them?

Mirco 14th October 2020 - 5:02 pm

Is it compatible with MAVLink and Arducopter firmware?

PaulSol 2nd September 2020 - 9:28 pm

How to Setup Camera Control.
You can start/stop recording and navigate through OSD menu using the switches on your radio. Here is how to set it up.
This is just part of the manual, no personal experience.
Did you check if it works? Can you start/stop record from remote via UART?

Scott Powdrill 31st August 2020 - 6:02 pm

Anyone know were to get the latest firmware? Dont seem to be listed on the site?

Oscar 4th September 2020 - 4:37 pm

I’d share it, but I already deleted the firmware file when I was clearing out old files a few weeks ago.
Maybe try to contact their customer service to get a copy sent to you?

Stephen 23rd August 2020 - 4:25 pm

I have this camera and it’s developed a problem where the recording stops by itself after only 5 seconds or so. Anyone else seen this? Using a fast v30 microsd and connection seems secure. Does it sound like a loose ribbon cable? Sometimes the image goes b/w also. Have ordered a separate 5V 3A BEC and a new Samsung micro SD card to try that.

Ralf 12th August 2020 - 9:00 pm

This Camera has a Sony 13 MP image sensor, why isn’t it possible to take photos with it?

Oscar 17th August 2020 - 7:18 pm

Because it’s designed for FPV

Jordi 13th July 2020 - 10:02 pm

Hi Oscar,

Great review, congratulations and thanks for all information. I would need your support to clarify the Image Quality point: when saying “Field of view is wider, especially in FPV mode” and “Colors in FPV feed are much nicer to look at, more natural”, are you referring Split 4 over Split 3 (you mean 4 has wider FOV and much nicer to look at than 3)?

Thanks in advance,

Oscar 21st July 2020 - 1:00 pm

Yes that’s correct. You can see more of the environment in the 4.

todd 7th July 2020 - 5:07 pm

Thanks for the clarification on FPV being standard res.

qemay 7th July 2020 - 12:33 pm

The yellow wire is only for FPV which is a standard NTSC/PAL SD res. The HD/4K res is only recorded on the SD card.

Mikhail 7th July 2020 - 11:41 am

How hard is it heated?

Oscar 8th July 2020 - 11:10 pm

Not too bad, I was holding the camera (main board) in my hand during the testing.

Popwax 7th July 2020 - 7:26 am

Is the sensor in native 4:3 aspect ratio and stretched to 16:9 for recording (like GoPro SuperView)? If it’s true, is it possible to record in native 4:3 aspect ratio without stretching?

Oscar 8th July 2020 - 11:09 pm

As far as i know this is not possible in the Split series, but possible with the Runcam 5 series (box camera).

todd 7th July 2020 - 12:23 am

Doesn’t having just a single wire (yellow one) coming from the camera limit you to non-HD output (like a TV’s composite output)?