1 pointThe IBIS should work, yes. If the adapter don't communicate the focal length to the camera you can manually select it. This was how it worked with the A7sII and I don't see how the A7sIII should be different. The menu on the A7sII was not as bad as people say it is in my opinion, and it looks like the menu on the A7sIII is even better. I would not worry.