How Film Deteriorates
While the choice between digital film moviemaking may be one of personal preference, what we do know for sure is that film reels have a much higher risk of being damaged or destroyed over time than their video counterparts.
As the plastic and emulsions age and are exposed to elements like light and temperature, colors fade and images may denigrate. The culprit is often something called nitrate deterioration. Until the early 1950s, most American movies were recorded on cellulose nitrate film. When the nitrate deteriorates, film often shrinks and begins to give off various acids that separate the emulsion from the base, yellow the individual still photos and make the film so brittle that it eventually crumbles and turns into dust. High temperatures and humidity can speed this process. While the acetate film versions that followed are also subject to decay, modern polyester film is believed to have a shelf life of hundreds of years [sources: Library of Congress, Kodak].
It's not necessarily the Hollywood classics at risk of being destroyed because many of these films have already been restored and transferred to digital formats. Instead, it's the lesser known independent and avant-garde works, along with old newsreels, documentaries and silent era flicks that have been scattered across the country over the years. Experts say these "orphan films," which were outside the scope of previous restoration and preservation projects, are important because they provide insight into what life was like in the days they were shot and recorded [source: National Film Preservation Foundation].