Most of the professional 360 rig solutions expect you to use GoPros, which, at $400-500 a piece, are simply not an option for me. Research and comparison led me to the Xiaomi Yi, a $75 camera with specs that rival the $400 GoPro. It's got nearly everything I want in a camera for VR, namely:
This was a huge factor. This technology is going to keep evolving over the next few years – I don't need something future-proof, I need the best value I can get for my money today. Especially when considering 6 or more cameras, the Yi's $75 price tag was a huge plus.
To ensure good sync between all cameras, we either need cameras that can start simultaneously (genlock), or we need to shoot at a high enough framerate to sync in post. I've found that shooting with the Yi at 60fps is enough for good sync in most situations – when synchronizing 60fps footage in post, clips can only be out of sync by at most 1/120th of a second.
The higher the better. The Yi natively does 1920x1080 @ 60fps, and can be hacked to shoot 2304x1296 @ 30fps or 1600x1200 @ 60fps. I shoot at 1600x1200 because 4:3 aspect ratio uses the entire image sensor for greater field of view.
Field of view
Following the formula I listed in my rig design post, I knew I needed at least 90° VFOV for a 6-camera cube rig. This ruled out the Mobius Action Camera with its 132° diagonal FOV (87° VFOV). The Xiaomi Yi, with is diagonal FOV of 155° (100° VFOV), provides plenty of overlap & makes stitching easier.
Especially at 30fps, the Yi produces a great-quality image with a desirably flat color profile. At 60fps, the image is a little murkier and more susceptible to low light (twice the framerate means the shutter only admits half as much light per frame). Shooting on a bright day, plus downsampling and sharpening in post, can mostly alleviate this issue.
Of course, the camera has downsides:
Like all action cameras, the Yi is limited by its battery life. I'm able to take about an hour of footage before batteries start to die.
Another issue common to all action cameras – I wouldn't use the in-camera audio for professional gigs.
Xiaomi Yi lenses sometimes arrive slightly out-of-focus from the factory. Out of the 18 cameras I purchased, I chose to refocus eight – only two of those were pretty bad. I followed an online tutorial to open the front of the camera, remove the glue connecting camera to lens, and refocus the lens while monitoring in real-time through HDMI out.
Lack of inbuilt professional controls
Unlike GoPro, the Xiaomi Yi lacks a 'Protune' feature to lock white balance or exposure. This would be a big plus for any multi-camera VR rig, but I haven't been unduly handicapped without it. There's a very active modding community at DashcamTalk who have hacked the Yi firmware to unlock higher bitrates and resolutions, and advanced controls like white balance and exposure lock.
All things considered, the Yi was the only camera that ticked all my boxes. If budget wasn't remotely an issue, I'd pick the Hero 4 Black - but with comparable specs to the $400 GoPro Hero 3+, the Yi really is great value for the money.
Here are the pros and cons to other popular options as I see them:
GoPro Hero 3+
Pro: Comparable specs to Xiaomi Yi
GoPro Hero 4 Black
Pro: 2k 60fps, ProTune
Pro: Smaller size good for rig construction
Con: Stock lens has low FOV, no 1080p 60fps