Going below f/2.8 introduces vignetting (light fall-off) and sharpness fall-off in the corners.
Going above f/11.0 introduces sharpness fall-off and contrast fall-off.
I might even hesitate to go above f/8.0, if I'm truly after the best possible results.
One has to wonder how those two would fare on the Nikon D850 body, as the Canon 1Ds mk3's sensor doesn't really let those lenses shine.
In any case, those are beautiful lenses and they certainly live up to the hype.
Now, If only Zeiss added VR/IS and AF - that would be swell.
Or even better - combine those two into a single 55-85 zoom lens.
Ahhh...one can only dream.