After working with the Metabones adapter for the Sony A7r with my Canon lenses for awhile, I've decided to write a review or my experiences anyway.
From what I was reading on other Amazon reviews or video reviews of this adapter with the Sony A7r I was under the impression that this thing was perfect, that everything was great, or at least acceptable.
And although it does work great for what I do, there are a lot of problems that I've encountered. It's a great adapter but using it is a little bit of high maintenance.
For every day photography I find the adapter to be a little cumbersome. It's slightly too slow at autofocusing for it to be used for every day street photography. But for landscape photography where you don't need autofocus it's great.
It seems to spend a lot of time seeking and making micro adjustments. It makes it just a little too slow for any moving subject matter.
I've tested auto exposure speeds side by side with my Zeiss 35mm lens and notice absolutely no noticeable difference in autofocus.
Camera Interface and Control
I also have and seen other reviewers have issues of it not working. Mine quit working after a week or so and I didn't know why. But I figured out a reason and solution. After messing with the unit I noticed that if the any of the screws on the back of the mount get lose even the slightest, the adapter would lose F stop functionality and eventually quit working all together. This creates a bit of maintenance and work. I have to always make sure I always carry the hex bit to check tightness so it doesn't give me problems mid shoot.
Issues I have when the screws are lose are:
-Flashing Fstop reading or loss of F-stop control.
-Images under exposed or the exposure not being correct to my camera settings.
-Record randomly stops when in Video Mode.
All around it's not a bad unit. My goal was to get it so I could have more lens options for my Sony A7r and it gives me that support. But for everyday use I still stick with my Zeiss Sonnar 35mm lens.
As far as image quality, there is no loss. I also don't notice any extra chromatic aberrations on ultra wide lenses as I've seen others report.
Image Samples of Metabones with Canon Lenses
Canon 70-200mm f2.8L IS II
Canon 16-35mm f2.8L II
Samyang 14mm f2.8
CAnon 24-70mm f2.8L