.. to add some more initial thoughts to the a7rii :
focus with canon lenses is much poorer than i expected and than many others commented.
I dont own many af canon glass, but the few ones i have dont work well. Its the 85/1,8, the 80-200/4 is and the 100-400 i tried. With all three i seem to have bad luck, with the metabones4 ( with newest fw ) they are very slo focussing or seraching forth and back.
I have two nice contax lenses with techart af adapters, a 45 and 90mm. They didnt work very well on the a7r1, on the a7r2 both work somehow better, but still far away for the native emount lenses. These focus very good now, as i described already.
Rainer,
Those are the reasons why I won't be buying an A7RII. I've got a bunch of Canon glass which is currently redundant, just sitting on the shelf. I'd like to use these lenses with a high-resolution, high-DR sensor. The Canon 5DSR was initially an attractive option.
My only full-frame Canon body is the original 5D. An upgrade from 13mp to 50mp, including all the other nice features of the 5DSR which the 5D lacks, would be really worthwhile, except that my new standard is now the performance of the Nikon D800E. The increase in resolution from 36mp to 50mp is not nearly as significant, in my opinion, as the loss of over 2 stops of DR, comparing the 5DSR with the D800E.
In general, whenever I make a decision to upgrade my camera equipment, such decisions have to relate in some respects to some sort of dissatisfaction I've experienced with my current equipment and the resulting images during and after processing. I never buy something simply because it's the latest and greatest.
I've already had the experience of trying to use the Nikkor 14-24/F2.8 zoom with adapter on my Canon 5D. The difficulties I experienced resulted in my buying a Nikon D700, mainly in order to get better functionality with that superb Nikkor zoom. That was the beginning of my switch from Canon to Nikon.
After reading so many reports of the lack of full functionality with so many Canon lenses on the A7RII, I would contemplate buying that camera for use only with a native, E-mount lens. Such a lens would have to address in some way the dissatisfaction I've experienced with my existing lenses, without introducing further dissatisfaction in other respects, such as excessive cost, bulk, weight and inconvenience.
The sort of lens that could fit the bill is the Sony 24-240, if it were sharper, because it has a useful range that I don't currently have among any of my Nikon or Canon lenses. However, introducing further dissatisfaction of the nature of soft edges and corners in the frame, and perhaps unacceptable softness at the long end, if that is the case, would be like taking one step forward and another step backward. What's the point?
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