[youpii]

Honestly I think that most Leica M lenses don't work out very well on digital cameras.

 

It's a known fact that most of the M-mount wide angles are very bad on the A7r.

Lens rental's explanation is that the thin glass (about 2mm) protecting the sensor exacerbates the angle of the light rays hitting the sensor for lenses with a short exit pupil (basically the wide angle lenses with a rear element very near the sensor).

They even worked with the creator of the "speed booster" and measured the loss of sharpness when the speed booster was used on a sensor without the protective glass because the speed booster was designed with that extra glass in mind.

 

So it's quite interesting to see that Zeiss also claims to have corrected the effects of sensor glass thickness.

But it's odd that there's no official statement about this in the product description, except "specifically designed for Sony α7 cameras".