Microfilm
About Microfilm
A microform is a scaled-down reproduction of a document, typically either photographic film or paper, made for the purposes of transmission, storage, reading, and printing. Microform images are commonly reduced to about 4% or 1⁄24 of the original document in diameter and more than 500X in size. For higher storage density, greater optical reductions up to 150X may be used.
Three formats are common: microfilm (reels), microfiche (flat sheets), and aperture cards. Microcards, also known as "micro-opaques", a format no longer produced, were similar to microfiche, but printed on cardboard rather than photographic film.
In addition to filming from original paper documents, equipment is available that accepts a data stream from a computer and directly produces a microform; the system exposes film to produce images as if the stream had been sent to a line printer and the listing had been microfilmed. The process is known as computer output microfilm or computer output microfiche (COM).
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