"When a writer and a director have different aesthetic starting points, compromise is impossible. It will destroy the very conception of the film. The film will not happen. When such a conflict occurs there is only one way out: to transform the literary scenario into a new fabric, which at a certain stage in the making of the film will come to be called the shooting script. And in the course of work on this script, the author of the film (not of the script but of the film) is entitled to turn the literary scenario this way or that as he wants. All that matters is that his vision should be whole, and that every word of the script should be dear to him and have passed through his own creative experience. For among the piles of written pages, and the actors, and the places chosen for location, and even the most brilliant dialogue, and the artist's sketches, there stands only one person: the director, and he alone, as the last filter in the creative process of film-making."
[Andrei Tarkovsky]