"What is film"constitutes the core issue of Bazin's film ontology.The photographic image serves as the pre-film form of"film-existence",and the authenticity of the film with spatial authenticity at its core is the necessary prerequisite for"film-existence"."Full film"represents the future imagination of"film-existence".Bazin's ontological thinking permeates the past,present,and future of"cinema-existence",and some of his assumptions and conclusions are highly consistent with the development of digital images and digital movies in the 21st century.His film theory and thinking are far from obsolete and can still bring enlightenment and reflection in the present.