What issues come up when evaluating film as historical evidence? How can we know that an early film is authentic? What does the film show and how might its images have been manipulated? Finally, what are film's strengths and weaknesses as a historical record?
A recent experience will help explore these questions. A producer preparing a film on Teddy Roosevelt sent me a bit of film (transferred to video). He doubted the film's authenticity, and asked me to judge the nature of the images it contained. An authentic image of Roosevelt, particularly one not well known, would be rare and valuable evidence. Given the physical deterioration of early film, I was likely to be viewing a later print, made either from the original negatives or by duping (photographing a film to make a copy rather than making a positive print from the original negatives) a positive print. These processes not only remove the physical material of the original film but can also change the framing of the image and contrast of tones. (Read more about the physical properties of film). Duping reduces an image's clarity, and sometimes duped prints go through several generations -- a photograph of a photograph of a photograph -- and lose clarity at every point.
These changes are compounded when viewing a film electronically, whether on video or computer. The original frame area may be altered to fit the screen, cutting off essential information. The proportions of the film frame most frequently found on video monitors and computer screens is based on the film frame that existed until the 1950s, when theatre owners widened movie screens to compete with television. Because of the overspill built into most monitors, film images lose information from their left and right edges when shown on a monitor, and color can vary greatly when color film is transferred to an electronic format. Film images hold more information, and more detail, than current electronic modes of presentation (except for high definition TV) can display.
In other words, the film image as it was originally produced may have undergone an enormous number of transformations before we actually look at it. While these transformations can make studying film difficult (for example, if the footage of Teddy Roosevelt had been duped so many times that I could hardly see his facial features), knowledge of them allows historians to make use of films as historical documents. Therefore film documents must be treated with the same skepticism and scrutiny that you bring to any evidence. In the case of the Teddy Roosevelt film, the footage was in black and white and had the same original proportions as the monitor, so some distortion was minimized. Although some clarity of detail was missing (probably due to both duping and the transfer to video), the images were still recognizable.
Understanding a film as historical evidence requires informed judgement based on knowledge from outside of the film. The Teddy Roosevelt footage showed a mustached, bespectacled man in a hunting suit and pith helmet waving from a hill. This was followed by a shot of African natives looking off-screen, as if frightened, then a close-up of Roosevelt as the "great white hunter." It is well documented that in 1909 Roosevelt went big game hunting in Africa and took a cameraman with him to record his exploits. Could these images be authentic documentary evidence of that hunting trip? Two clues led me to confirm the suspicion that the film was staged. First, the figure, while clearly made up to resemble Roosevelt (the glasses, the mustache), did not really match other photographs of Roosevelt from this period. This was an actor portraying the former president. Second, and perhaps most important, the cut to the African natives indicated images that had been arranged to give the impression of simultaneity -- to indicate that the natives were looking at, and reacting to, Roosevelt). But the hunter and the African natives were almost certainly not filmed at the same time (the lighting and backgrounds of the two shots did not match). This points to one of the aspects of filmmaking most significant in the use of film as historical evidence: film cutting or editing.