Film perforations

Film perforations, also known as perfs, are the holes placed in the film stock during manufacturing and used for transporting (by sprockets and claws) and steadying (by pin registration) the film. Films may have different types of perforations depending on film gauge, film format, and intended usage. Perforations are also used as a standard measuring reference within certain camera systems to refer to the size of the frame. Some formats are referred to in terms of the ratio "perforations per frame/gauge size" to provide an easy way of denoting size.