This review on using Leica M lenses on the Sony A7r 36mp camera is by Tom Grill (Web | Blog, click on images for larger view):
As a Leica owner, I was immediately intrigued when I saw the first announcements of a full-frame, small, 36mp, mirrorless camera from Sony with the ability of accepting Leica M lenses. It sounded a bit like a Leica aficionado’s holy grail for a second camera body: a high resolution, full-frame body with a higher resolution than a Leica M, and costing only a third the price of the Leica M 240. Of course the real question was how the Leica M lenses would perform on the A7r body. There wasn’t much concern for the longer focal lengths. These generally adapt with little or no problems. The big question was how the wide, and especially the super-wide angle lenses would perform.
The A7r does have micro-prisms on its sensor intended to deal with those sensor areas where wide angle lens problems could be expected to occur. Nonetheless, the Sony A7r could not be expected to have the built-in firmware corrections for any aberrations these lenses might display.
