I am expecting M poison only. So far no one mentioned the Zeiss ZM lenses, they are not poisonous?
A lot of the RF lenses got issues on the A7/r.
A7s appears better for some. (verdict is out there, since its new)
Even some 50mm lenses don't sharpen up to 'good' levels at f5.6 and f8.
So imagine, walking around in Chinatown and you see the Buddha Relic temple for the first time... "Wah!" you say and proceed to stop down f8 and capture the temple, but find that the edges are soft.
I have tried the following :
J8, J8m, J3, H103; - all edges considered 'no good'
Leica Summicron 50mm DR - edges only 'ok' at f5.6 while most SLR 50mm would already be at 'excellent'
Industar 61 - no issues
Leica Elmar 50 f2.8 (collapsible) - very good at f8 throughout the frame (I was impressed)
Before anyone says that the problem lenses are the cheapie Russian ones, these lenses all work well on film with the usual characteristics of 50mm lenses (very sharp edge to edge by f5.6 )
Zeiss Biogon designs - color cast, vignetting, edge smearing issues (well documented online)
If you only shoot shallow DOF stuff, then these are non-issues.
But personally, I only use the lenses for interest, size, rendering wide open or near wide open.
If I wanted all round reliable wide open to stopped down, I will go for SLR lenses.