INteresting to read this, and particularly this below
From what I've found testing with a couple lenses is, if your not in close and use a focus point other than the center one the camera has a hard time hitting focus. If you use the center focus spot and recompose the focus will be much much better but still softer than shooting in the center of the lens.
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I was having this issue with the 55/1.8. Center point it likes for most lenses, and the 55mm was having hunting issues at night. I noticed that if you focus on a vertical subject like a door way, it cannot lock focus with back light, but as soon as there is horizontal intersection in the shape, it can lock on quick.
Honestly, overall, having the A7rII for about a week, with the 35/2.8 and 55/1.8.... the lenses, and the way it focuses, for the price seams a bit "toy-ish".
I do love the images it can make.... when I have the chance to reshoot and actually get the shot :-) But I am still practicing.
A interesting YouTube video on this lens line up I watched today was from a tog called Darren Miles in Florida. He does some nice lens comparisons, and I recommend you take a look at his observations.