The standard MFB-1A Film Insert accommodates both120 and 220 film types. To switch between film types, simply twist the film pressure plate. Film type and exposure number are visible in a window on top of the MFB-1 Film Back.
The optional MFB-1B Vacuum Film Insert offers a flat, stable film plane when shooting with 220 film. The MFB-1B uses the Real Time Vacuum System, first developed for the Contax RTS III, to pull the film down to the pressure plate. The film is pulled down just before the first curtain of the shutter travels and is released right after the second curtain has traveled. This system operates in Aperture Priority, Shutter Priority, Manual and X modes.