Get Zeiss Touit 12mm at B&H Photo.
See the earlier work with the Zeiss Touit 50mm f/2.8M on the Sony A7R.
The Zeiss Touit 12mm f/2.8 Distagon is nominally an APS-C lens, but like all lenses it “covers” more than that size.
- Zeiss Touit 12mm f/2.8 Distagon Usable Image Area on Sony A7R
- Zeiss Touit 12mm f/2.8 Distagon on Sony A7R: Classic Aspect Ratios
Includes HD and UltraHD images from f/2.8 through f/16 for 3:2, 4 X 5, 6 X 6, 4 X 3, 6 X 17 aspect ratios.
The 12mm f/2.8 is an interesting ultra-wide option for the A7R. The discussion includes a handy table of usable dimensions and aspect ratios on a full-frame sensor
It appears that one can get very useful ~15.4mm equivalent field of view on the full frame Sony A7R with the Touit 12mm f/2.8 Distagon. The UltraHD series show very clearly what one can expect for image quality outside the nominal APS-C coverage area.