Abstract: This invention relates to a device in a movie film apparatus for intermittently feeding flexible perforated film past an optical system a unit length at a time comprising a film support for guiding a strip of perforated film for exposure to an optical system, a detent on said film support, said detent having a front film sliding face that slopes in a direction having a component in the direction of film feed, said front film sliding face of said detent being engageable by perforations of film as the film moves in the direction of film feed to temporarily stop forward motion of the film in advance of the detent and form it into a loop behind the detent which increases in size with film feed and decreases the angle of attack of said film at said front film sliding face of said detent, triggering means for exerting a triggering force against the outside bowed portion of the loop when said loop reaches a predetermined size to slide the end of said loop at said front film sliding face of said detent substantially