I use (only) manual focus lenses with my a7 and a7r. Now I prepare 4k resolution images and I am really satisfied.
I have 35 lenses, and I use all of them. Contax-Zeiss are among my favourites (with Leica-R, Meyer Gorlitz but also other ones): I know and I use 18 distagon, 50 1.4, 60 makro-planar (what a game with leitz 60 macro), 85 1.4 (here I prefer the Leitz 80 summilux), 180 Sonnar, 300 tessar. ever a pleasure, great lenses.
I used also the new 55 sonnar f/1.8 for sony, but I prefer the 50 planar Contax....
All the best,
sandro