I finally got some 220 film to try out the 220 film back that I'd purchased for my "new to me" Bronica ETRsi. I found out the hard way that, unlike the 120 film backs I have, I was able to shoot off a roll of 220 with the dark slide still inserted! With the 120 backs, even if you advance the film - if the d/s is inserted you cannot fire the shutter. Quite helpful for "newbies" already baffled by the gear. Does anyone know if I just have a defective back - or is this a strange "feature" of Bronica 220 filmbacks?