Microfilm

First generation microfilm is produced by microfilming from original, usually print, sources. First generation films are used for long term preservation and to produce second generation films. Second generation microfilm is produced by making a copy from a first generation microfilm before
it is stored for preservation. Second generation films are used to produce user copies (‘third generation’ films) on microfilm or microfiche, and more recently for making digital copies through scanning. Second generation films can have either a positive or negative polarity. See also:
Microform polarity.