In article , philg@rolex.ai.mit.edu says...
>Canon T/S is vastly more convenient to use than Nikon (shift only)
>because the diaphragm is automatic. It is truly painful to shoot
>casually with the Nikon PC lenses because you have to stop down >manually for each shot, then open back up for composition and focusing.

I agree that the auto diaphram of the Canon shift lenses is more convenient than the preset diaphram on the Nikkors, but in practice,
I find the one-finger operation of the preset ring very easy and
quick - not really a problem. BTW, in answering the original post, I forgot to mention that there are Schneider PC lenses for the Leicaflex, also.
Hope this helps.