[davidmanze]

As mentioned in the review, the distortion correction has taken a toll in terms of border IQ.

However, this doesn't explain it all.However, the Pana MTFs for the 12-35mm f/2.8 also suggested a much better performance than what we saw here in the lab as well as out there.

 

The problem with these manufacturer MTFs is that you just don't know the parameters.  So maybe these were obtained in fairy tale land where the witch had too much sake and the engineers stole the magic wand.  

   Oh right I know the one, the magic wand that stirred the gin and tonics!