If you have found your film mysteriously advances on its own in your Diana or other medium format camera, then this simple modification could fix it in 10 seconds.
One of the small but significant frustrations I’ve experience with my Diana F+ is that sometimes the film seems to advance on its own. You wind on after your last shot and leave it neatly aligned with the next number. Then when you check before taking your next shot you realise that the film has moved on and the number isn’t even visible any more. At the least is going to leave you with a smaller gap between frames, at worse, overlapping images (assuming you don’t want this). I know I’m not the only one to have this issue as there is plenty of moaning on Flickr and I also found the solution there thanks to user .Scribe, but seeing as no one has written anything here I thought I should share it.
The problem specifically, is that unlike the take up spool which only moves when you turn the film advance knob, the feeder spool is free to rotate slightly. If you have your Diana knocking around in your bag, the film can go a bit slack and wind on a bit. To fix it you need to put a bit more resistance in the feeder spool, without stopping it moving when you actually do need to wind on.
The really simple solution comes in the form of the folded end of a 35mm film box. Just tear off a flap, then fold the two sides in to the middle. Then make a small hole in the middle of the card and stick it over the small knob that sticks out of the bottom of the Diana back. Now, when you load film and put the back on, the card pushes gently on the bendy arm that holds the film in place and stops in from moving unless you want to wind on.
I’ve got through over 10 rolls since trying this and the film hasn’t budged a millimeter without me making it.