This Sigma adapter is a great investment for newer model Sony Alpha series E-mount camera systems (A7II, A7RII, A7SII, A6300, A6500). I have not tested the adapter on my A7R and A6000, but I am sure that the performance would not be that great based on the type of focusing system in those cameras. I currently shoot with a Canon 6D and 7DII and own a fair amount of Canon and other EF mount glass. I currently own an A6300 and just recently picked up an A7RII and decided to get this MC-11 to mount a few of my Sigma Art lenses. The focusing performance on these two cameras with the Sigma adapter is very near the performance of native Sony E-mount lenses. There are a few things that do not work, such as eye auto focus, but realize that we are adapting an EF mount lens on a Sony camera system and certain things just aren’t going to work.
Remember that Sigma will only guarantee functionality with updated Sigma Art lenses and state that other brands and older Sigma lenses are not compatible. However, I have mounted a Tamron 24-70 and was able to achieve fairly reliable autofocus. It’s not great performance, but it does work. I have also used a few Canon EF lenses with similar results. There are a few lenses that flat out do not work such as my Tamron 70-200. So, when it comes to using other than Art series lenses you run a 50-50 on the lens working with the adapter. At this point in the game I really do not have anything to complain about on this adapter. It is a cheaper alternative to some of the other adapters out there and for the most part it works really well and is as advertised.
The price point of this adapter is what got me interested in the Sigma adapter. There are other adapters on the market, but I’m not sure they can compare to the Sigma’s performance.