Microfiche is one of the most compact analog storage media in common use. It is normally used to provide a comprehensive research library in institutions (such as small college libraries) that could not otherwise afford the floor space.

Each microfiche card holds about 100-130 pages depending on the size of the original. A library of 20,000 microfiche, 10,000-20,000 books, fits in a cabinet about 1.5x0.5x2 meters. Some companies specialize in providing such libraries to institutions.

Microfiche is normally used to keep copies of books, and sometimes for periodicals and newspapers. Its most standard form is a clear plastic card, about 10cm (4in) by 15cm (6in). Usually the title of the work is in visible lettering along one edge. The most common reduction ratio is 24x, with 7 rows of 14 page images each fitting on a single microfiche. Some microfiche have a digital indexing system exposed on the edge of the card, or each image, but these data are not required to use the microfiche, but rather to support automated retrieval systems.

Microfiche is not as widely used as Microfilm.

The medium has numerous advantages:

1. It is compact, with far smaller storage costs than paper documents. Generally, a book or a year of a periodical fits on one fiche and takes 0.05% of the space and weight of the paper work.
2. It is lower cost than a paper copy. Most microfiche services get a bulk discount on reproduction rights, and have lower reproduction costs than a comparable amount of printed paper ($5 per fiche in 2003).
3. It is a stable archival form. Most library microfiche use polyester with silver-halide dyes in hard gelatin, with an estimated life of 500 years in air-conditioning. In tropical climates with high humidities, fungus eats the gelatin used to bind the silver-halide. In the tropics, diazo-based systems with lower archival lives (20 years) are preferable, because they have polyester or epoxy surfaces.
4. Since it is analog (an actual image of the original data), it is easy to view. Unlike digital media, the data format is instantly comprehensible to persons literate in the language; the only additional equipment that is needed is a simple magnifying glass. This reduces the possibility of obsolescence.

The principal disadvantage of microfiche is that the image is too small to read. Libraries use special readers that project full-size images on a ground-glass screen. A significant disdvantage is that when stored in the highest-density drawers, it is easy to misfile a fiche, which is thereafter unavailable. Some libraries therefore keep the microfiche cabinet in a restricted area, and fetch fiches on demand. Some fiche services use lower-density drawers with labelled pockets for each card.

Another disadvantage, is that a conventional photocopier cannot reproduce the images. Libraries using microfiche often have a few viewers that can produce a photocopy of an image, for a nominal fee.

The final disadvantage is that microfiche can only be reproduced a limited number of times, while digital media regenerate and often include error detection and correction schemes.

Originally most microfiche were produced by first making microfilm with a microfilm camera. After developping the film, it was cut into short strips which were usually inserted by hand in a microfiche jaquet. The jaquet could after that be reproduced any number of times.

In the 1970s and 1980s machines were developed which could produce microfiche directly from a computer peripheral. These microfiche were called COM, for Computer Output Microfiche. They were used to distribute massive amounts of frequently changed data to institutions or companies which could not afford computer terminals but already used microfiche readers for a variety of reasons. In some cases the quantites involved justified getting a microfiche reader just to read COM fiche.

External links

• The Library of Congress Photoduplication Service (http://www.loc.gov/preserv/pds/)
• The Northeast Document Conservation Center (http://www.nedcc.org/plam3/tleaf51.htm)