Having just acquired a non "N" 645, I can consistently get 16 frames per roll if I don't align the start arrows with the pointer. I set the arrows so they are just visible as the roll unwinds. The frame spacing is 8mm between frames. The film doesn't wind out until the shutter is pressed with the frame counter showing 16. The camera does this with either a 120 insert or a 220 one with the key flipped around. Is winding the film out after hitting the shutter button on frame 16 normal on anyone else's camera? Just wondering if this is normal for this model or ? ? ?. I'm not complaining, the manual says 15 frames per roll, so an extra frame per roll is a nice unexpected feature. Arista.edu films don't work very well as the paper leader is conductive enough to pass enough current from the spring contacts to the film rails to tell the camera there is no film in the insert. The odd thing is the paper backing is not conductive on the inner surface from the point where the film is taped to it. The camera works perfectly with Fuji, Kodak and Ilford films. 220 inserts appear to work perfectly with 120 film if you reverse the plastic key between the spool clips. There appears to be no difference in the inserts other than the sticker on the latch. I measured the pressure plate force on both inserts I got with the body and a third 220 one, the deflection force was within 10% for three different backs. . A super nice camera overall.