Microfilm was a physical storage media – typically 16-millimetre (0.6-inch) or 35-millimetre (1.4-inch) film – upon which images were reduced in size to a fraction of their former selves. This allowed documents, photographs and video footage to be shrunk, copied and stored for both secrecy and greater longevity. For example, historical paper documents were very vulnerable to moisture, but when imaged and placed on film they became all but impervious to it.
Often batches of documents were placed on one large sheet of microfilm with a readable code on top referred to as a microfi che – the code enabled the documents to be identified immediately. Viewing the stored image was achieved with a slide/film-based projection system (as pictured) that was similar to the overhead projectors we use today.
While microfilm is still used in select applications, the invention of the computer and virtual media has largely left it obsolete, with documents, images and films now copied and backed up on discs or cloud storage.