Microfilm is a kind of photographic film used to make extremely small copies of print documents and other materials. Because these images are greatly reduced in size, microfilm can store large amounts of information in a small space. Microfilm comes in rolls, whereas microfiche consists of similar images arranged in sheets. Microfilm and microfiche are collectively referred to as microform.
The process of making microform copies is called microphotography. Microphotography uses special copy cameras or computer-controlled devices that write the image to the film or fiche.
The material recorded on microfilm is read with a microfilm reader. This machine enlarges the images on the film and projects them onto a built-in screen. Some microfilm readers, called reader-printers, can also produce a paper copy of the enlarged image. Microform scanners can create digital (numerically encoded) copies or prints of the enlarged image.
Uses.
Before the development of computers and electronic record keeping, people commonly used microfilm to store and view documents of all kinds. Libraries stored newspapers and magazines on microfilm, reducing their storage needs and the risk of fire. Banks kept records of checks by storing an image of each check on microfilm. Governments stored census data on microfilm.
Information once kept in microform is now routinely stored in digital form and even made widely available over the Internet. But microform still serves as an important backup to digital storage. For example, microfilm can survive some natural disasters, such as floods, that destroy digital records. With proper processing, handling, and storage, microform can probably last hundreds of years.
Types.
Most microform consists of high contrast black-and-white images with few or no shades of gray. Some microform can show continuous shades of gray or even color.
It is common to find microfilm in rolls 16 millimeters (5/8 inch) wide and 100 or 215 feet (30 or 65 meters) long. A 215-foot roll can hold many documents reduced in size by 20 to 50 times. Rolls of microfilm 35 millimeters (1 3/8 inches) in width were preferred for large documents, such as engineering drawings.
Microfiche measures 105 by 148 millimeters (4 1/8 by 5 13/16 inches). The images on a microfiche are arranged in a grid pattern. A single microfiche may contain images of up to 400 pages reduced by 18 to 72 times. A form of microfiche called ultrafiche features images reduced by 90 times or more. A single ultrafiche may contain 1,000 document pages.
