i have been trying out a v5 summicron 50mm (the one with the collapsible hood) on the a7rII and it works very, very well. there is no colour smearing at all and at f2 there is just a hint of edge softness in the extreme corners, at 2.8 and below it's sharp across the board, lovley bokeh at f4-5.6. i had the sony 55mm and although it is outstandingly sharp etc. etc. it never inspired me. the summicron on the other hand is a little gem on this camera. IMO.