Tap to AF or AFC?

[Bunraku]

This is regarding filming rather than photography, but are most of you guys using AF and tapping the screen or pressing C1 or C2 or doing AFC mode?

I did AFC yesterday for my first film and although my central subject was clear, the sides were soft? If you look at the video below you can see the boats at back right looking slightly blurry compared to the palace.

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I suspect i'll change to AF with TTF, but surely that will still make the part of the screen not selected soft?

Thanks