I know this is an old thread, but as a fellow Panon AIII owner, I can confirm. There seems to be some confusion on this issue based on other models by the same maker. The shutter speeds can absolutely be changed at any time on this model. In fact, I find it far easier to wind the shutter at a faster speed, so that the turret turns faster, and then reset the speed slower if needed. I personally use the 1/2 second setting a lot, and resetting the shutter at that speed takes a long time. I will switch it to 1/50 or 1/200, wind it, and then reset it at 1/2 if I’m using that slower speed. I believe I have a scan of the actual manual somewhere, but it really isn’t that informative. Film path is indicated on the removable film gate assembly. New users be aware that the spools go under the spring clips, and that you don’t miswind it so that the spring clips touch the film itself. They only contact the back of the backing paper. Pay attention when loading, as this was confusing to me at first, as I didn’t properly visualize it. Depth of field chart can be important. I posted one from a slightly newer PANOX model years ago on flickr for reference. It’s accurate based on my experience, but doesn’t include f22.
Hope this helps someone.
Tony