Film is generally sold with a 'use by date'. This can be considered as the final date that any guarrantee that the film performs to specification ends. Obviously the film still works and depending on how it is stored it can perform to specification for some time. It is generally accepted that the colder the environment seal film is stored in, the longer it will last.
For various reason many films are not used by this date. From not selling to being stuck in a draw and forgotten. Being a chemically produced product film does deteriorate, but very slowly. Especially for colour films this can have some interesting effects when the film is finally processed.
For black and white films the processing methods have not changed since the dawn of photography. So very old black and white film can be use. Obviously getting a result is not guarranteed.
Colour films though have a different history. The first genuine colour films became readily available in the 1930s. Each manufacturer though had there own processing method and these tended not to be compatable. Even films made by the same manufacturer might need different processes.
There are two types of colour film. Negative and positive. The first delivers a colour negative from which a colour print can be produced. A positive however is a colour transparency that is not a negative. This can be used directly. While prints can be made from positive transparencies their main application was a slides and cine film.
As processes improved and changed over the years a number of different films and processes were introduced. Usually at any given time a manufacturer had a colour print requiring one process and a colour transparency requiring another. Kodak had two different process for slide a cine film. Sold under the general name of Kodachrome these colour films had to be returned to a very specialist laboratory for processing. There was no way such films could be processed at home or in a small processing unit. Ektachrome was the name Kodak used for a range of films that could be processed by smaller units, and latterly by the amateur at home. Colour negative films have always required less sophisticated processing technology.
In the early days of colour film transparency films at least were normally returned to the manufacturer, or an approved agent for processing. Initially this was not considered a monopoly situation, but as colour film became established the combining of film sale and processing became a problem in some countries.
Over time the manufacturers consolidated colour film processing to two. One for colour negatives and one for colour slides. Because of their major influence on the industry these were orignated from Kodak and today colour print films are processed to negative in chemicals referred to as the C-41 process and colour slides in chemicals called the E-6 process. The latter requires more precise operation than the former and usually requires the services of a specialist laboratory to process. E-6 though can be used by an amateur as well. C-41 is usually processed in one machine called a mini-lab and such processing services are more common.
For out of date film the developing situation means that only films designed for C-41 or E-6 can be processed. It is now impossible to process Kodachrome films. Processing to older systems may still be offered by certain specialists, but they are very few and very expensive. For the amateur out dated colour films need to be C-41 or E-6 compatable.
It is possible to process other out of date films in black and white chemicals to produce a black and white image, but the results can be very variable. Practically tests needs to be carried out on a sample to determine processing times.
As film does deteriorate over time this means that the sensitivity is reduced. So depending on age a film sold as 400asa should be rated at 200asa or even 100asa. A rough rule of thumb is one stop for every 10 years.
The consequences of aging seems to vary between films. My efforts with out of date colour film have tended to result in an overall colour cast for slide films, and a general deterioration with a bit of colour cast for negative films. Interestingly today it is very easy to obtain prints from both film types using scanning and electronic image processing.
Follow the links below right to examples of out of date film in use.