This is a small stream that is fed by a spring and defines one edge of my property. This is a test shot with my new 24-70mm f/2.8L II. It is a full frame shot from my 1DX. It was shot RAW and not sharpened. It seems the lens is fine to me. The corners look good and I see no evidence of decentering. This is with AFMA at 0. What do you folks think? The focus point was on the stream bed in the center of the frame.

1DX
24-70mm f/2.8L II @ 24mm
Tripod
ISO 3200
f/13
1/640