To what extent is a film director the 'main author' of a film?

The concept of authorship in cinema is a discourse fraught with a variety of ideological, commercial and practical questions and tensions. In comparison to literature, where it is commonplace for a novel or poem to be 'authored' by one person alone, film is a fundamentally collaborative process and medium. The vast majority of films (be they independent or studio productions, short or feature length) are the result of directors, writers, cinematographers, performers, editors and more, all working together towards a finished product.However, even with this in mind, film has and continues to be produced, sold and theorised in relation to the efforts of lone (often male) figureheads which, more often than not, are directors. 'Auteur theory' or 'auteurism' can account for this to a certain extent, with film critics, theorists and historians elevating the efforts of directors like Alfred Hitchcock, Akira Kurosawa or Federico Fellini to the pantheon of great artists. Indeed, this sentiment stems from the discipline of Film Studies' roots in literary studies and its own preoccupation with and reverence for romanticised literary authors (Shakespeare, Dickens, Tolstoy). Putting to one side the merits of identifying individual artistry, we must also consider the purely commercial benefits that arise from being able to sell a film on the name of its author/director alone, which the promotional strategies used to market films by the likes of Quentin Tarantino, Christopher Nolan or Steven Spielberg readily demonstrate. As such, any discussion concerning authorship in film must consider, not just the artistry of a selected personality, but the ideological, commercial and industrial forces which shape the hierarchies of power and control implicit in creative roles such as 'Director'.