I recently bought a Bessar RF to dabble in what this sort of camera can do. It has been both a revelation and a frustration. My problem is uniform focus across the image. The lens seems to swing a little to one side (probably as a result of the design that allows it to fold ;-) ) . There is some play there, but it fells much less than a degree of movement. I'm used to movements with my 4x5 camera and given that I use a 90mm lens (not unlike the 105 Skopar on the Bessar) I don't think this amount of 'free play' is enough to account for what I'm seeing.
For example, with this image
it seems that focus is just 'poor' at the edges, however close examination shows that its actually a tilt ofthe focal plane (camera in portrait orientation).
Looking at the top right in more detail a pine tree quite further back which is in focus while the pine needles of "my tree" are starting to fuzz up badly.
Looking at the middle of the focal plane the "my tree" is in focus, but the middle of that pine tree above is out of focus (consistent with the DoF created with f8).
then looking further to the bottom its apparent that the focal plane is comming closer to the camera
While this has some advantages in some orientations, I think I would prefer to have the focal plane at a more predictable and "normal" orientation.
So, does anyone have any suggestions on how to fix this? I'm having trouble seeing this effect on a ground glass and loupe I made up, so this will make 'adjustment' tedious.
Aside from that, its a nice camera!