Sony A6400: 4K Recording and Face Detection

Yesterday I ran head long into the first limitation of the Sony A6400 camera which had me rather baffled for a little while and involved a fair amount of poking around to try and resolve.

The problem

The Sony A6400 has a fantastic auto focus with fast and accurate face and eye detection. I saw lots about this in reviews and it was one of the primary reasons for choosing the camera. I anticipate recording videos of myself and want to allow the camera to find my face and ensure it is in focus for the duration of short "pieces to camera".

Unfortunately, the A6400 is not capable for detecting faces at the same time as recording 4K while also outputting a feed using HDMI or when Bluetooth is enabled.

This was a bit of a pain for me because I was relying on using an external display to preview the output.

Workarounds

There is not a single solution for this because the camera simply cannot do what we want to do. However, there are some workarounds which may work for you. I'll document them here so you can decide if any of them are suitable.

1. Upgrade to the Sony A6600 which supposedly can overcome this problem. It's a fairly significant price increase. I was not aware of the limitation of the A6400 when I bought it and, if I had, I may well have considered going for the A6600.
2. Use the built-in screen rather than trying to output to HDMI. Not really much of a solution but might work well enough. However, you cannot use the remote control features because you have to enable Airplane Mode too.
3. Record using 1080p rather than 4K. Do you really need 4K, anyway?
4. Don't record 4K content on the camera and record it on an external device instead. See below for details on how to do this.

Recording 4K content to another device

To do this, you're going to need something that can actual handle the recording. There are few options out there. I happen to have a Blackmagic HyperDeck Studio Mini which can do this. It's not the most portable of devices though but will work for me as it can live in my "tech lab". It's only input, however, is SDI so I will need 4K compatible HDMI to SDI converter.

Before you can do this, you need to Enable Airplane Mode. This will disable the bluetooth and is required to enable this. Go to the MENU, then navigate to the Network tab, then page 1 and then choose Airplane Mode.

Once you've got a device, you'll need to configure the camera to not try to record to the memory card. To do this, go to the MENU and open the Setup tab (the 5th tab, in yellow). Navigate across to page 4 and select 4K Output Select and then choose the appropriate HDMI only option based on your frame rate. More details can be found on the Sony Help Guide (which, incidentally, is the page that tells you what features will be disabled if you try to record to the memory card).