007 - Microform (R)

One-character alphabetic code that indicates the category of material to which the item belongs is microform. Microform is a generic term for any medium, transparent or opaque, bearing microimages. A microimage is a unit (e.g., a page) of textual, graphic, or computer-generated material that is contained on aperture cards, microfiche, microfilm, microopaques, or other microformats and that is too small to be read without magnification. Microforms may be reproductions of existing textual or graphic materials or they may be original publications. A fill character (|) is not allowed in this position.

Card with one or more rectangular opening(s), or aperture(s), specifically prepared for the mounting or insertion of a piece of photographic film containing one or more microimage(s). The cards are usually EAM (Electrical Accounting Machine) punched cards, commonly known as IBM cards, that are standardized for use in card-handling machines. Such cards contain only one aperture and most frequently have only one microimage.

Consists of a strip of photographic film wound onto a single core (or hub), housed in a protective container. Microfilm cartridges require reading equipment (readers and reader-printers) that is specifically adapted for their use. Normally, the end of the film is left free for threading into such equipment. Common film lengths, widths, and reduction ratios are the same as those of microfilm reels.

Analogous to the sound tape cassette. Consists of a strip of photographic film wound onto a double core, housed in a protective container. Microfilm cassettes require reading equipment (readers and reader-printers) that is specifically adapted for their use. Because they are double-cored, they are not threaded when used in such readers and reader-printers. Usual film lengths are 100 ft (approximately 30 m.) or less. Common film width is 16 mm. and usual reduction ratios are those of microfilm reels and cartridges.

Consists of a strip of photographic film wound onto an unenclosed flanged holder (or reel). Microfilm reels require manual threading when used in readers and reader-printers and require equipment that is adapted for their use. Film lengths are usually 100 ft. (approximately 30 m.) or less. For microimages produced by filming textual and graphic materials, the most common film widths are 35 mm. and 16 mm. and reduction ratios commonly range from about 10:1 to about 20:1. Sixteen millimeter film with effective ratios of either 24:1 or 48:1 is most often used for COM (Computer-Output-Microfilm) microimages.

Transparent sheet of photographic film containing microimages arranged in a grid pattern (a two-dimensional array) and having a heading that contains identifying information in text that is large enough to be read without magnification. Grid patterns vary with reduction ratios.

Sheet of opaque material bearing a number of microimages arranged in a two-dimensional array. Microopaques resemble microfiche. Common dimensions are 3x5 in. and 6x9 in. Common reduction ratios are approximately 24:1 or 20:1. Microopaques usually have identifying information in text that is large enough to read without magnification.

A short strip of microfilm cut from a roll.

A wound length of microfilm not on a reel, cartridge, etc.

Special material designation for the microform is not specified.

None of the other codes is appropriate. Some microform types that use code z include:

Includes microforms such as microchips, microdots, and microform scrolls.

Lines and characters appear dark against a light background.

Lines and characters appear light against a dark background.

Mixture of positive and negative images.

Polarity of the microform is not known. (Some colored negatives may appear to be positive if the colors of the original are not known.)

Height and width of an aperture card in inches or centimeters.

Dimensions are not known.

None of the other codes is appropriate.

Less than 16:1 ratio (less than 016).

Between 16:1 and 30:1 (016-030).

Between 31:1 and 60:1 (031-060).

Between 61:1 and 90:1 (061-090).

Over 90:1 (over 090).

Reduction ratio is not known.

Not all parts of the microform have the same reduction ratio (e.g., the contents of two books may be microfilmed onto one piece of film; the type face on the books may differ, so that one of the books may be filmed at a 14:1 ratio and the other at a 18:1 ratio).

Image is in black-and-white (usually black-and-transparent).

Has more than one color.

Combination of one-color and multicolored images.

Color of the microform is not known.

None of the other codes is appropriate.

Emulsion is a compound of silver and halogens. Silver halide microforms always appear black-and-white (black-and-transparent).

Emulsion consists of sensitized layers composed of diazonium salts that react with couplers to form dye images. The color of the image is determined by the composition of the diazonium compound as well as the couplers used in the process and may be black, violet, or another color.

Light-sensitive component is suspended in a plastic layer. On exposure, the component creates optical vesicules (bubbles) in the layers. These bubbles form the latent image. The latent image becomes visible and fixed by heating the plastic layer and then allowing it to cool. Vesicular films are commonly blue or beige in color. They do not appear to have much contrast (very high density) until projected in a microform reader.

For example, a microfilm may have slices of film with one type of emulsion and other slices with another type of emulsion.

Item does not have emulsion on film.

Emulsion on the film is not known.

None of the other codes is appropriate.

Camera master or COM recorder master.

Any generation employed mainly for the production of other microforms.

Microform made from another microform that is intended primarily for use rather than for production of other microforms. Always used for microopaques.

Made up of a combination of generations of film.

Generation aspect is not known.

Type has not been identified.

Acetate safety base film whose exact type cannot be determined, i.e., where it is unknown if the type is diacetate or triacetate.

Cellulose diacetate film base. Introduced before World War I for home movies, diacetate base was more expensive and unpredictable than nitrate base and so failed to gain acceptance in professional 35 mm. film production. Diacetate film base was at times used for microfilming of documents.

Cellulose nitrate film. Cellulose nitrate support or base was used in the manufacture of 35 mm. film (and some 17.5 mm. film) until 1951. Nitrate base film is no longer manufactured. Nitrate film base was at times used for microfilming of documents.

Combination of nitrate base and safety base film. The use of mixed bases, spliced together, can be found in microforms from the early 1950s.

Microform on a reflective rather than a transparent base.

Film base is made of a synthetic resin (e.g., estar). During the 1980s, it became the most widely used base for microfilming of source documents.

Mixed safety base films are spliced together; no nitrate film.

Cellulose triacetate film base. Cellulose triacetate is a high acetal compound with very low flammability and slow burning characteristics. From 1951, triacetate has been used for professional as well as for amateur produced moving image film. It has also been used at times for microfilming of documents.

Base of film of the microform is not known.

Bone of the other codes is appropriate.