In this paper we present OntoFilm, a core ontology for film production. OntoFilm provides a standardized model which conceptualizes the domain and workflows used at various stages of the film production process starting from pre-production and planning, shooting on set, right through to editing and post-production. The main contributions in this paper are: we discuss how OntoFilm models the semantics necessary to interpret these workflows consistently for all users (Directors, DoP's, grips, post-production, lighting). We also discuss how our ontology forms a common bridge between the low level descriptive metadata generated for the video footage and the high level semantics used in software tools during the production process.