9.5 mm film

9.5 mm film is an amateur film format introduced by Pathé Frères in 1922 as part of the Pathé Baby amateur film system. It was conceived initially as an inexpensive format to provide copies of commercially-made films to home users, although a simple camera was released shortly afterwards. It became very popular in Europe over the next few decades and is still used by a small number of enthusiasts today. Over 300,000 projectors were produced and sold mainly in France and England, and many commercial features were available in the format. The format uses a single, central perforation (sprocket hole) between each pair of frames, as opposed to 8 mm film which has perforations along one edge, and most other film formats which have perforations on each side of the image. The single hole allowed more of the film to be used for the actual image and in fact the image area is almost the same size as 16 mm film. The perforation in the film is invisible to viewers as the intermittent shutter... full article at wikipedia