I know that has been discussed to death but thought this may be of some interest. I have both Zeiss and Leica lenses available for my A7r. I prefer the Leica lenses because of their weight.... the whole idea was to get the overall weight down for easy travel. However I found that my Zeiss lenses because of the added weight AT THE CAMERA provide additional dampening with beneficial results. I have yet to find any difference in vibration tests with a change of tripod - Gitzo 3 vs the little Traveler makes no difference. Attaching a heavy bag from the center column makes no difference. But there is a dramatic difference between the Zeiss lenses and the Leica lenses because of their weight/mass..... and because its at the camera it has a dampening effect that gives me a 2/3 to 1 stop advantage. So any added mass at the camera is beneficial which includes the Sony adapters and associated lenses. I recall Guy posting that he has had very little difficulty with his Zeiss 135 which weighs in at 2lbs. The added mass is very beneficial but I reckon that Guy still has to be very careful.....
Victor
Victor