Importance

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Abstract

In a camera having an exposure gate and a transport for transporting film past the exposure gate, the film having a series of perforations along at least one edge of the film, wherein the number of the perforations are an integer per exposure frame, the film having a substantially transparent magnetic layer at least in the region of the perforations, a mid-roll change apparatus. The mid-roll change apparatus includes a source of a steady-state magnetic field located downstream of the exposure gate and adjacent to the series of perforations for magnetizing the magnetic layer between the perforations as film is transported past the source; a magnetic field sensor located upstream of the exposure gate and adjacent to the series of perforations for sensing fringing magnetic fields emanating from perforation edges, the area between which have been magnetized; and a perforation sensor located to sense the series of perforations of the film.

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First Claim