ANSI AIIM-TR13-1998 pdf download Preservation of Microforms in an Active Environment – Guideline
4 Types of microforms Microforms come in a variety of materials, shapes, and sizes. Some microformats are no longer produced, but since large collections of these exist in many libraries, they have been in- cluded here.
4.1 Transparent microforms
4.1.1 Roll microfilm “Roll microfilm” is a generic term for microfilm contained on reels. Generally the film is 16 mm or 35 mm wide, although it is possible to have “Scroll Microfiche” on a reel that is 105 mm wide. Most reels found in libraries, archives, and infor- mation centers contain a maximum of 100 ft (30 m), although the length can extend to as much as 155 ft (47 m) depending upon the thick- ness of the film stock. Roll microfilm is some- times housed in cartridges or cassettes.
4.1.2 Microfilm jacket A microfilm jacket is a flat transparent, flexible carrier formed by affixing a support-sheet to a thin image-forming layer, forming one or more channels, made to hold one or more pieces of image microfim, and with a heading area. (ISO defini- tion.) The active (or working) copy is generally a diazo or vesicular film duplicate of the original jacket.
4.1.3 Aperture card An aperture card is a card with one or more apertures specifically designed to hold a chip of microfilm before or after imaging. (ISO.) The card contains frames from a roll of 16 mm or 35 mm microfilm that have been cut and mounted or inserted into the aperture card. This card can also contain keypunched, or interpreted, or preprinted information or a combination for identification and retrieval of the infommation. Frames of 35 mm microfilm mounted on aperture cards are com- monly used for architectural and engineering drawings and for maps.
4.1.4 Microfiche A microfiche is a microform in the shape of a rectangular sheet having one or more microi- mages usually arranged in a gnid pattern, with a heading area across the top. (ISO.) Common sizes include 75 mm x 125 mm (nominal 3in x 5in)and105mmx148mm(nominal4inx6in).
4.1.5 Computer-output microfilm (COM) Computer-output microfilm (COM) is microfilm containing data produced by a recorder from computer-generated electrical signals. (MFT.) It may be produced in roll microfilm format or mi- crofiche format.
4.1.6 Ultrafiche (also known as ultr-fl/m) Ultrafiche (also known as ultra-film) is microfiche with images reduced more than 90 times. Com- mon sizes include 75 mm x 125 mm (nominal 3 in x 5in) and 105 mm x 148 mm (nominal 4in x 6 in).
4.2 Opaque microforms None of the opaque microfom formats is cur- rently being manufactured, although some may still be sold. Where there is a choice, transparent microforms should always be purchased rather than opaque microforms, because the quality of the image is better with transparent microforms, and because obtaining satisfactory equipment for reading and printing from opaque microforms is difficult now.
4.2.1 Microcard A microcard is a 75 mm x 125 mm (nominal 3 in x 5in) card with up to 40 photographially pro- duced microimages per side.