Most people, at one time or another, discover a roll of exposed film from a long-ago vacation and wonder what treasures lie within, or they find a valuable unused roll just waiting for use. Whether you have a number of canisters of unused film or simply some exposed rolls lying around, there are a few things you should know about that film before having it developed--things that may very well save the important photos that you've taken or are contemplating.
What Film Is
Common photographic film is a sheet of thin plastic, coated with an emulsion containing light-sensitive materials of different densities. When exposed to light, an invisible image is transferred to the plastic where it waits until processed in a mixture of chemicals to create a visible image.
Generally, all new photographic film from a manufacturer is marked with an expiration date between one and two years in duration. This is because the emulsion starts to break down over a certain amount of time. Degradation of the chemicals may cause the image captured on the film to slowly deteriorate over time becoming foggy or losing contrast.
Extending Film Life
There are ways to extend the life of your film by many months or even years. Chilling film and reducing the humidity will slow aging and prolong the film's usefulness. Refrigerated, factory sealed film can effectively change the period of usability to between two and five years. Freezing film also is an option and essentially stops the aging process. To freeze film, seal it in a zip-lock bag and remove as much of the air as you can. When you're ready to use it, thaw the film slowly and naturally by letting it reach room temperature before use (this applies to refrigerated film as well). Only thaw the film you plan to use at any one time.
Heat and Humidity
Whether or not you plan to cool or freeze your film, you should also be aware of what to explicitly avoid environmentally to safeguard your film. Just as a cool, dry environment can prolong the life of film, heat and humidity can equally take its toll. Avoid storing film in extremely hot areas--never in a car, or on a windowsill--and if the film is already loaded in the camera the same rules apply.
Developing Old Film
Black and white film can be surprisingly robust and forgiving, and develop to produce prints of perfect quality even decades after being exposed. Color film, on the other hand, is not nearly as stable and can produce color shifts as it ages. If you have very old color film--or film damaged environmentally--consider taking it to a specialty processing professional. It costs more in some instances but the extra care developing it can sometimes save the film. Taking it to a one-hour lab likely will doom old or damaged film.
The Bottom Line
Although not guaranteed by the manufacturer, film can actually sit for some time before developing. The newer the film stock used the better in almost every respect. But if you find yourself with newly discovered film canisters or more film than you can use right away, take steps to properly preserve it and you can keep that film for a considerable amount of time before finally developing it.