Over the weekend I took some shots of a series of lampposts. To get the framing I wanted whilst keeping them vertical, I had to raise the camera slightly, tilt the back back to the vertical and then employ as much rising front as I could before the bellows stopped me.
I used a 6x7 roll-film back on a 4x5 back, so the framing was not at the absolute edge of the lens' (Rodenstock APO Sironar-S 150mm, if it helps) coverage.
Before stopping down, I checked (and, I'm 99% sure, re-checked) the focus with the lens wide-open on the front lamppost. I then stopped down to f45 so would have assumed that the focusing would have been safe anyway. But when I developed the film, the same lamppost was distinctly fuzzy at the very top of the frame.
I thought of three possible reasons...
1. I cannot focus properly. Whilst always a possibility, I would've thought that f45 would cover most sins in that department.
2. The roll film back (a Horseman) had buckled the film slightly. But I took a few frames of the lampposts (for filters etc) and all of them were iffy. Yet I used the back for other shots and there didn't seem any problem at all with them.
3. There's an issue with "extreme" camera movements and stopping down that I haven't considered... when stopped down I could not really check the focus properly as it was a little dark, so this seems the most likely to me.
Answer / suggestions / comments to help me go back this weekend and get a printable negative are greatly appreciated!