I think you reproduced my result but in a different way. In the IXMOO the film is not hold back by any friction of the cassette opening (felt tip) since the IXMOO cassette is in OPEN position inside the camera once the base plate has been locked. What happens in my case is that every other frame the film "jumps" exactly one hole over the sprocket wheel, widening the frame gap by that distance. My explanation is that the tension of the film is increased inside the IXMOO canister by advancing it lets say for two frames and then since nothing holds it back releases the tension like a coiled spring, which makes it jumping over the sprocket wheel.
In my case it also happened with films that have a very thin film base but are in standard film canister (with felt tip). I did not have this problem of irregular gaps with standard film (eg Delta400) in standard film canister.
My camera is in for service at DAG since last year and I hope that Don can figure out a solution.
Originally Posted by michaelwj
Just to dig up an old thread for a bit of a rehash.
I received a "user" M4 recently, and all was going well until the last roll where I had a bonus sprocket gap between frames. I remembered this thread and thought it might have the answer but while reading it I think I worked out what happened...
Typically I load the camera, advance of shoot a blank, check the rewind spins and then I'm done. But this time (mainly cause it's a new to me camera) I was playing around with it, and wound the rewind knob until it didn't wind anymore, like you would at the beginning of the roll to take up the tension. When I let it go the tension spun out of the film and the rewind knob spun pretty quickly. The gap is at this point (I developed the film that night and remembered playing with it between the two images) and I'm guessing that the tension coming out of the roll pushed the film over the sprockets. It was only in the one place.
I'm using Fomapan 400 bulk rolled onto generic plastic cassettes (gotta get me some IXMOO's). Interestingly the felt is not so tight on that cassette as I had a bit of a light leak on the first frame from the light getting trough the trap (it was a 35 degree day in the midday sun, sunny 22!).
Gabor, did you find the cause of your issue?