How to Choose the Right Codec on the a7S II
Codec choice is always a thorny conversation. This one isn’t supported as well by that program. That one doesn’t compress movement as cleanly as that one there. The Sony a7S II is certainly no slouch on the codec choice front, but that can just exacerbate the whole situation. So when should you record with what codec? Well…
AVCHD - The Legacy Option
In the long-ago days of 2014, Sony released the a7S and the world was forever changed. It recorded to both an AVCHD codec and a shiny new XAVC-S codec, and it was glorious. AVCHD is a fairly standard codec that any editor will recognize and your NLE is guaranteed to accept. And while that safety option may have been welcome at the initial launch of the a7S, it becomes less and less relevant as time goes on and XAVC formats have become more supported.
XAVC-S - The Best Option
Let’s not beat around the bush here. XAVC-S supports the highest bit rates, the highest frame rates, and the highest resolution. It is a newer technology that, if most side-by-side tests are to be believed, resolves detail much more sharply and compresses moving objects much more cleanly. B&H has a great side-by-side comparison about halfway down the this page.
One potential problem with this format is that it can only be recorded to “Extreme Capacity” SD Cards, commonly shortened to SDXC. Those cards are 64gb or larger, and absolutely mandatory for XAVC-S recording. When in doubt, SanDisk has a helpful guide to what you can and cannot use.
MP4 - Why is it Here?
The inclusion of MP4 on the a7S II is a confusing choice by Sony. Like AVCHD, its bit rate is capped and its recording options limited. But unlike AVCHD, it is not a particularly favored post-production codec, and any use it would have as a compatibility failsafe is minimized by the inclusion of AVCHD. Most likely, it was included as an olive branch to amateur filmmakers or non-technical vloggers who came to the camera on reputation alone. Not many other explanations make sense.
While AVCHD was once a great titan of the recording codec world, it is slowly being phased out by newer and more efficient codecs like XAVC-S. Is it still usable? Yes. Will it still produce great results? If used properly, sure. Could you be doing so much more if you shot in XAVC-S? Most definitely.