Microfilm is photographic film (normally black and white) with a reduced image.
It differs from film used in conventional cameras not only in the fact that the image is reduced,
but also in the quality of the image. The emulsion on the film is formulated to produce high contrasts between the text and the background rather than the more subtle shadings common in regular photographic film. This facilitates the reading of text, but it reduces the quality of illustrations which may appear on the material reproduced.
Microfilm is produced in long lengths of film of varying widths, most commonly either 16mm (about 5/8 inch) or 35mm (about 1 3/8 inch). Generally the film is spooled onto reels which can then be mounted on the equipment. The images are read by shining a light through the film and projecting the image through a magnifying lens onto a screen. Lenses are available in several magnification strengths and can be interchanged in the equipment, as needed, to provide the desired legibility.
Microfiche(plural form = microfiches )
Microfiche uses the same filming technology as microfilm, but rather than being produced on long rolls the film is cut into flat rectangular sheets usually about 4 by 6 inches in size.
Each fiche can contain up to 98 images which are generally arranged horizontally from left to right like a book.
Commercially produced microfiche have eye readable headers which are used for filing and retrieval.
Microfiche is read using the same light and lens technology as microfilm, and the same equipment can be used for both. Microfiche is placed flat between glass plates in a movable frame which can be manipulated to view the images.
Microprint and Microcard [known generally as micro-opaques ]
When a negative is printed onto photographic paper rather than film the product is called a micro-opaque. Each copy is printed by offset lithography rather than being reproduced from the original film. This is older technology that has virtually disappeared from the market, but library collections still contain millions of these items. The terms microprint and microcard are used to denote different sizes of micro-opaques:
|microprints are large cards measuring about 5 by 7 inches.
|microcards are smaller, measuring about 3 by 5 inches.
Micro-opaque images are read by reflecting light off the image rather than through it as is the case with microfilm and fiche. As a consequence, microprints and microcards cannot be read on the same equipment as film and fiche.
From: Boss, R.W. and Raikes, D. (1981). Developing microform reading facilities . Westport , Conn. : Microform Review Inc.