In this age of digital video, it’s easy to forget that until recently movies were all made and released on film. The Library of Congress’s digital preservation blog has a discussion of “Digitizing Motion Picture Film”, though this title doesn’t fully represent the ongoing debates. Some people, the article notes, think that film is still best preserved with film. Even now when a terabyte of data costs less than dinner for four at Denny’s, it takes a lot of bits to preserve movies at full resolution.
The digital option includes many different possible formats. The article broadly distinguishes between “scanned film” and “video” formats. DPX, the leading scanned film format, digitizes each film frame separately and doesn’t include audio, though it may include optical soundtracks. It assumes that sound will be stored separately. “Video” formats typically use compression techniques that take advantage of the similarity of one frame to the next and allow some loss, and they normally have integrated audio. DPX isn’t a suitable format for playback, but it can offer better digitization quality at the cost of larger file size.
The Federal Agencies Digitization Guidlines Initiative (FADGI) draft, “Digitizing Motion Picture Film: Exploration of the Issues and Sample SOW [Statement of Work],” is worth reading for an overview.
It isn’t directly relevant to digitization, but as an old-movie fan (or maybe as an old movie fan) I’m fascinated by the guidelines for handling film to be digitized. I’d known that nitrate film is a serious fire hazard, but hadn’t known about the “Vinegar Syndrome,” the tendency of acetate film to break down into acetic acid over a long period.