How Film Restoration Works

Until a couple decades ago, moving images were captured exclusively using photochemical film. You know, the stuff that comes in those big reels and that you have to hand-feed through a projector to get on the big screen. These days, however, more filmmakers are turning digital production techniques to shoot and screen their pictures. While the differences in the final product may be subtle to the untrained eye, the two techniques vary widely.

The film used to capture moving picture images has two components: A light-sensitive emulsion and a plastic base. Here's how Kodak explains it:

The emulsion is a type of gelatin composed of silver halide crystals. A camera records images by transferring photons of light onto the film as it rotates behind the lens. The crystals turn into silver metal when exposed to the light and form a photo image during the film development process. The series of photos captured on the film can be seen individually once it's developed and create a moving picture when the film is run through a projector [sources: Kodak, Side by Side].

Digital recording, on the other hand, uses an electronic sensor to capture an image, rather than a chemical process. The light that travels through the camera hits the sensor's pixels, creating a number of individual electronic charges that together create an image. The images are stored as data, which can be transmitted via discs, flash drives and the like [sources: JISC Digital Media, Side by Side].

The film vs. digital debate is currently raging on just about every movie studio lot from New York to LA. Film purists often say that they like the gritty, granular feel that comes with the old-fashioned method. Academy Award-winning cinematographer Wally Pfsiter called switching from film to digital "trading oil paints for a set of crayons." Those who have embraced the technology, meanwhile, tout the immediacy of the process. Instead of shooting a scene and waiting to see what it looks like once the film is developed, directors and actors can see what they have right away. Director Robert Rodriguez has compared digital to film by calling the latter technique "painting with the lights off" [sources: JISC Digital Media, Side by Side].

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].

The actual restoration work is a treasure hunt of sorts in which film archivists go searching for the early versions of the film that they want to bring back to life. The goal is to create what's called a "pre-print" copy of the original film: a master copy of the film as it once was [sources: UCLA, The Picture Show Man].

That means first locating the cleanest copy of the film that's still available. Under ideal circumstances, that would be the original negative version. That's the film that was actually reeled through the camera and used to capture the images. It's called a negative because the original film captures the image in a backward form that includes only shades of the true colors. It's later used to create a "positive" version that ends up on the screen. You need a negative to make a positive print and a positive to make a negative print. Every duplication means a loss of quality.

For many films, there are various trial, correction and distribution copies that may be floating around and could be used for restoration. More obscure pictures – those with just one or a few copies – are often more difficult to restore because there are simply fewer versions of the film from which to choose. On the other hand, more popular films raise their own hurdles to restoration because of the wear and tear endured by the negative as a result of heavy copying.

Once the various versions of the film are located, the restorer may physically cut and paste them to create a full-length master. Wearing white gloves, he'll open the film can and gently wipe off any mold. Then he'll unwind the film slowly, flattening out any curl. Using special equipment and splicing tape or film cement, he'll join pieces of film together as needed. He'll also repair any broken sprocket holes [sources: NFPF]. The idea is to remove wear and tear so that viewers can enjoy the film in its original form rather than an enhanced version.

For a big-budget movie restoration, the film may go through a device called a wetgate scanner – a scanner that runs the film through a chemical bath that fills in any scratches on the negative. Then the film is converted to a digital image. High-end graphic and editing computers can adjust the pixels so faded color becomes rich; they can also remove damaged frames of film or scratches and dirt on individual frames. This is painstaking work. It may take three or four hours to fix one frame [source: Popular Mechanics].

The audio track may also be enhanced. In the case of the "Jaws" restoration, the mono track was upgraded to include two additional rear speakers, creating a surround sound atmosphere for home viewers [source: Popular Mechanics].

And one last thing after the restoration project is complete: Another negative is created so the film will be properly preserved for posterity.