[Klaus]

Good but short of superb

http://www.opticallimits.com/sonyalphaff...y1635f28gm

Surprised to see your finding of low field curvature.  The several copies I’ve tested had immense field curvature on the edges of the frame noticeable up to f/8, which was really the only negative I could find.  Need to be very careful about composing landscapes with highly variable depths.

The best center and best borders/corners were mostly in the same frame.
So any softness that we've seen came from performance but not field curvature.
That being said - this may differ across the focus range.