Preservation microfilm is intended to be permanent, and for this reason, three generations are produced: the camera or master negative, the print master negative, and the positive-use copy.

Camera negative
The camera negative should be regarded as the archival generation, and it should be used to produce one other negative for printing or reproducing positive copies. The archival storage of the master negative is important, as it ensures that the camera-negative quality is not reduced by generational loss or the making of multiple copies. The camera negative must be stored in a secure place remote from other film generations, and under consistent environmental conditions (see STORAGE).

Print master negative
The print master negative is used to create the original positive copy and any additional copies requested by outside libraries. Under no circumstances should the print master negative, or the camera negative, be used by readers.

Positive copy
The positive copy is what readers use. If the copy is of a popular work, such as a national newspaper, it can suffer considerable damage through careless handling and poor storage. Review of the positive copy is important so that new copies can be made from the print master when necessary. Some institutions are able to support the cost of their microfilming efforts through the sale of positive microfilm copies.