Rainer,
good to see you're still around at the forums.
All this brings me back to the first days of trying non Canon lenses on the Canon 1Ds, Mk2Mk3 5D 1-2-3.
Main reason is for this, Nikon didn't have a good full frame digital.
Then Nikon had the D3x, which I'm still using and does the job.
Now the Sony is the king of the hill.
What will happen next
Nikon 4DX with a new Sony sensor that will kill the rest.
New Nikkors PC lenses 17 - 24 - 35-45-85 ( Now that would be nice!)
Actually, the PC-E 85 is stellar anyway. I use it for all my product shoots.
Even the 45 PC-E is very usable,once you remove the CA.
The current 24 PC-E is certainly good enough, however the lens I use the most is the 14-24 Nikkor.
Love!
Happy shooting!
W