There are a lot of action cameras branded “4K camera”. Simple reason, they sell better wearing this logo. Although their output video size is 4K, it might not be real 4K. Find out about the difference about real vs fake 4k:
Real vs Fake 4K
What is real 4K?
Real 4K or native 4K is simply explained: the original source (sensor output) is 4K resolution.
What is fake 4K?
As mentioned at the beginning, “4K cameras” sell better. Therefore the original source at a lower resolution is upscaled to achieve a 4K output file. Upscaling uses known pixel values to estimate unknown intermediate pixels. This process works by guessing or “interpolating” values based on a weighted average of known pixels in the vicinity. In other words the sensor’s output is a lower resolution than 4K and then the image is upscaled by interpolation.
There is also another trick. If the sensor / processor is not capable of doing 4K at a reasonable frame rate, the frames are doubled to state a better figure on paper.
So how can you check if it is a real, native 4K camera?
Watch out which frame rate the camera can do in 4K. If it is less than 24fps it will be less fluent, more likely a stop motion video. Here’s an example of a 10fps 4K video, recorded with an EKEN H9 and an early firmware:
As mentioned at the beginning there is another trick: Doubling frames. 15 frames per second are recorded and each frame is doubled. The output file now shows 30fps, but it looks like 15 fps. You can’t tell from specs when browsing them, only when looking through your footage frame by frame. When there should be motion but 2 frames show the exact image, the frame was doubled.
4K resolutions is 4096 x 2160 pixels and is actually not 16:9. The 16:9 format (3840 x 2160 pixels) is called UHDTV (Ultra HD). Nevertheless if you multiply the pixels you’ll get a result of about 8,8 MP (4K) or 8,29 Megapixel (UHDTV). Which means if the sensor is smaller than 8MP, you can’t get a 4K video out of it. E.g. take the EKEN H9 which has a 4MP sensor (Omnivision 4689), but is branded 4K. Same applies to the Aptina ON AR0330 sensor.
Be aware, often cameras are advertised as 12 MP cameras, but the Megapixel just refer to the max. photo size. The EKEN H9 is sometimes advertised as 12MP camera, but just the max. photo resolution output is 12MP. As explained above also the photo is resized from the 4MP sensor! Therefore check the sensor type.
Why are there 12MP sensors? It’s more than needed fro 4K?
Most sensors have a 4:3 resolution. If you crop top & bottom of a 12 MP sensor to get to a 16:9 format, you will end up with the 8MP for 4K resolution. Cameras with larger sensors will benefit from a higher photo resolution. So what is done there? E.g. take the Canon 5D DSLR: with their first HD recording version, the Mk II, they binned (downscaled) the sensor output. Their latest version Mk IV crops the output source, which looks like zooming into the frame.
Even if the sensor offers more than 8MP it might not be capable of 4K resolution. Good example is the very common 16 MP Sony IMX206 sensor used in Git2, YI Action Camera 1 & SJCAM M20. When looking at the data sheet of the sensor, you can see that 4K output is not listed.
At this point compliments to GitUp and SJCAM as they integrated an 4K option to their cameras, but never advertised them as 4K camera furthermore indicate that 4K resolution is interpolated.
Processor / Chip
Not only the sensor, also the processor has to be capable of 4K video resolution. The famous Novatek 96660 chip used in many action cameras (SJ5000x elite, Firefly 6s or Elephone Explorer) is not capable of real 4K resolution. The highest resolution possible is 2880 x 2160 with 24fps. Sunplus 6350 (10fps) and Allwinner V3 (15fps) are also not capable of 4K resolution with a decent frame rate.
1080p 120 fps
That’s not a reliable method, but most action cameras which offer native 4K at 30fps, also offer 1080p with 120 fps. Action cameras offering fake, interpolated 4, mostly just offer 1080p with max. 60 fps. Therefore also check out the camera’s 1080p HD resolution.
Don’t get me wrong, “fake 4K cameras” are not bad cameras. Quite the opposite, many of them offer great results in HD and are reliable cameras. I just wanted to point out the difference between real and fake 4K. If you are fine with HD resolution, you can pick any of those cameras. If you insist on 4K resolution, be aware to get a real 4K camera. The results of fake 4K cameras – in 4K resolution – are not better than recoding in HD and upscaling the video on your computer.
Take a look at my article “Best 4K Action Camera 2016“, where I compare 4K cameras such as: GoPro Hero5, YI 4K Action Camera, SJCAM SJ7 Star and EKEN H8 Pro.