100% center crops at 50mm



Corner crops wide open.




Now at f/5.6, not a lot of difference for the Sony DT 16-105mm as it's only 1/3 of a stop down from wide open, yet interesting how the Sony Zeiss 16-70mm f/4 gets a lot more depth of field one stop down.



At f/5.6 there is no vignetting so we'll ignore the overall image, and see a drastic improvement with the Sony DT 16-105mm.



At f/8. I'd venture to say the Sony Zeiss 16-70mm is slightly front focused, or has some focus shift at 50mm.



 f/8 corners



As it seemed like the Sony Zeiss 16-70mm was front focused, I re shot the whole sequence at a later hour with the same parameters.



Corners wide open.



Centers at 5.6



Corners at f/5.6



f/8



Corners.



It's strange that at 50mm the Sony Zeiss 16-70mm f/4 has focus shift to closer objects on stopping down. This isn't too unusual with fast primes, but with a zoom it's typically masked by the depth of field.