In my opinion, movies would be weaker sources than written literature because of the discrepancies between an author's intended meaning and a movie's depiction of the book. The movie and the book are often different in terms of plot development and characterization.If you've ever read a book, watched the movie, and compared the two, you'd notice that the movie isn't a perfect imitation of the book. Events are thrown in or left out, or they play out differently than in the book. In addition, another person would be filming the movie other than the author, and they may interpret the theme(s) of the book in his o rher own way. It's always better to rely on the work from the original author instead of a movie.