In history, we learn that a chronicle is an account of what happened, while history is the interpretation of what happened. But a lot of history is also piecing together what happened based not on a single reliable chronicle, but based on all sorts of evidence and accounts. We have to remember, then, that history is somewhat removed from what actually happened; it is not simply what happened, but an interpretation of the meaning of accounts of what happened.
An historical novel is fiction based in history. It is not merely a period novel, but a fictionalized account of real history. It is a dramatized alteration of history.
And of course a film adaptation of a novel is a dramatized alteration a book.
Which brings us to a film I enjoy greatly, La Reine Margot. This is a period film about French history, centering on the royal family (and future king Henri de Navarre) around the time of the St. Bartholomew's Day Massacre.
But La Reine Margot the film is not based on historical accounts of this period, but is an adaptation of Alexandre Dumas' historical novel La Reine Margot, which is the Romantic writer Dumas' romantic re-interpretation and fictionalization of history. And that history that Dumas (most certainly rather liberally) interprets into his novel based on his era's interpretation (or application of meaning) to the time period explored is based on centuries of historical interpretation (and myth making) based on varied accounts of actual events.
And yet, in adapting Dumas' novel, it seems probable that the filmmakers of La Reine Margot also looked to history to create and alter the film, not merely relying on Dumas' fiction. And for the costumes and sets, they very likely turned to contemporary art, getting some of the characters to look as the 16th century painters made them look. Of course, the painters of the 16th century were not creating photographic likenesses either--artistic renderings of these royal figures were themselves interpretations imbued with meaning (the artists' meanings, and the desired meanings of the patrons).
So this brings us to a movie based on a book (but also likely based on history and art) based on historical interpretation of various accounts of actual reality.
The movie is an interpretation of an interpretation (also based on interpretations and interpretations) of various interpretations of various accounts of reality.