A microform is a scaled-down reproduction of a document made for the purposes of transmission, storage, reading, and printing. The original document is typically in the form of photographic film or paper. Four formats are common: microfilm (reels), microfiche (flat sheets), micro-opaques (like microcards), and aperture cards. In addition to filming from original paper documents, equipment is available that accepts a data stream from a computer and directly produces a microform.
John Benjamin Dancer was one of the first to produce microphotographs in 1839, using the daguerreotype process. Microphotography was first suggested as a document preservation method in 1851 by the astronomer James Glaisher, and in 1853 by John Herschel, another astronomer. Systems that mount microfilm images in punched cards have been widely used for archival storage of engineering information.
The medium has numerous features, including that it enables library users to access collections without putting rare, fragile, or valuable items at risk of theft or damage.
Desktop readers are boxes with a translucent screen at the front on to which is projected an image from a microform. A microfilm printer contains a xerographic copying process, like a photocopier. To create microform media, a planetary camera is mounted with the vertical axis above a copy that is stationary during exposure. Conversions may be applied to camera output or to release copies.
Description A scaled-down reproduction of a document is known as a microform. Typically, a microform is either photographic film or paper, and made for the purposes of transmission, storage, reading, and printing. Microform images are commonly reduced to (about 4.2%) of the original document in each dimension, which is in area. For higher storage density, greater optical reductions up to 200× (e.g. the Photo Chromic Micro-Image (PCMI) ultrafiches by NCR Company) may be used.
Three formats are common: microfilm (reels), microfiche (flat sheets), and aperture cards. Micro-opaques refer to a less-known format, similar to microfiche, but printed on cardboard rather than photographic film. Production of micro-opaques virtually ceased in the late 70s.
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).
Types of microform media
Flat film 105 × 148 mm flat film is used for microimages of very large engineering drawings. These may carry a title photographed or written along one edge. Typical reduction is about 20, representing a drawing that is . These films are stored as microfiche.
Microfilm 16 mm or 35 mm film to motion picture standard is used, usually unperforated. Roll microfilm is stored on open reels or put into cartridges. The standard lengths for using roll film is rolls, and 100 ft, 130 ft or 215 ft for 16 mm rolls. One roll of 35 mm film may carry 600 images of large engineering drawings or 800 images of broadsheet newspaper pages. 16 mm film may carry 2,400 images of letter-sized images as a single stream of microimages along the film set so that lines of text are parallel to the sides of the film or 10,000 small documents, perhaps cheques or betting slips, with both sides of the originals set side by side on the film.
Aperture cards
Aperture cards are Hollerith cards into which a square opening has been cut. A 35 mm microfilm chip is mounted in the hole inside of a clear plastic sleeve or secured over the aperture with adhesive tape. They are used for engineering drawings in all engineering disciplines. There are libraries of these containing over 3 million cards. Aperture cards may be stored in drawers or in freestanding rotary units. The key-punched holes enable them to be readily sorted using computers.
Microfiche A microfiche is a sheet of flat film, the most common and standard format is the National Microfilm Association (now Association for Intelligent Information Management) format which measures 105 × 148 mm in size (the same dimensions as the ISO A6 paper size) and utilize a reduction ratio of 24:1. It carries a matrix of microimages commonly read left-to-right and then top-to-bottom, while most COM microfiches are read from top to bottom, left to right. Most microfiches are read with the text parallel to the long side of the fiche, though some tables may be rotated 90 degrees requiring the use of the rotation mechanism of the reader (if present). Frames may be landscape or portrait in orientation. Along the top of the fiche is an eye-legible heading (sometimes with backing material to enhance contrast) carrying bibliographic information including fiche number, title, series, publish date, and publisher. The heading may also be color-coded to aid retrieval. The height of the banner varies with microfiche format and reduction ratio.
The most commonly used format for the contained microimages is a portrait image of about 10 × 14 mm. Office-size papers or magazine pages require a reduction of around 24:1 (in diameter). Microfiches may be stored in individual open-top envelopes. usually made of acid-free paper, which are put in drawers or boxes as file cards, or put into relatively big pockets and made to look like a book, or may be stored in specially-made binders with pages of pockets which show only the title bar of each fiche.
One special use case of microfiche is print-on-demand. When a researcher wishes to borrow a file on microfiche a copy is made on demand on diazo microfiche at very low cost. Thus the masterfiche never leaves the library and file integrity is guaranteed and the researcher can even build up a micro library at home in this way. However, this type of system obviously depends on the adequate provision of viewers.
Microfilm jackets Microfilm jacket is a special form of microfiche, roll films (usually 16mm) are first produced, then cut up and loaded into strips or individual frames in channeled plastic envelopes. They are used for filing systems where there's a requirement to update individual files (say, personal records)
Ultrafiche Ultrafiche (also ultramicrofiche) is an exceptionally compact version of a microfiche, storing analog data at much higher densities, (generally defined in the 70s as reduction rate higher than 90×). They are typically used for storing data gathered from extremely data-intensive operations, or for storing a book containing several thousands of pages on a single fiche. The "Microbook" Library of American Civilization, published by Library Resources Inc. (a subsidiary of Encyclopædia Britannica Inc.), used this degree of reduction to put more than 20,000 volumes on 3x5 inch ultrafiches, with each book occupying only one fiche and thus "unitized". In Britain, the British National Bibliography offered its Books in English service on ultrafiche at 150x with 2380 images per fiche. The development of ultrafiche is a breakthrough made possible by the development of a light-sensitive (photochromic) dye that is grain-less and light erasable. The PCMI micro-images are made first with photochromic dyes, then contact-printed onto a high-resolution photographic plate to make copies using conventional silver-halide film.
Micro-opaques Micro-opaques are opaque, non-reversed formats and require specialized readers that projects them using reflected light. Few companies manufactured them, two of the most famous are Microcard Editions Inc. (Microcard) and Readex Corporation (Microprint), whose product names became synonymous with the medium. They were invented in 1948 by Fremont Rider and described in his book, The Scholar and the Future of the Research Library.
History
Using the daguerreotype process, John Benjamin Dancer was one of the first to produce microphotographs, in 1839. He achieved a reduction ratio of 160:1. Dancer refined his reduction procedures with Frederick Scott Archer's wet collodion process, developed in 1850–51, but he dismissed his decades-long work on microphotographs as a personal hobby and did not document his procedures. The idea that microphotography could be no more than a novelty was an opinion shared in the 1858 Dictionary of Photography, which called the process "somewhat trifling and childish". Originally published in Dictionary of Photography (1858).
Microphotography was first suggested as a document preservation method in 1851 by the astronomer James Glaisher, and in 1853 by John Herschel, another astronomer. Both men attended the 1851 Great Exhibition in London, where the exhibit on photography greatly influenced Glaisher. He called it "the most remarkable discovery of modern times", and argued in his official report for using microphotography to preserve documents.Exhibition of the Works of Industry of All Nations 1851. Reports by the Juries on the Subject in the Thirty Classes into which the Exhibition was Divided. (London: John Weale, 1852).
A pigeon post was in operation during the Siege of Paris (1870-1871). René Dagron photographed pages of newspapers in their entirety which he then converted into miniature photographs. He subsequently removed the collodion film from the glass base and rolled it tightly into a cylindrical shape which he then inserted into miniature tubes that were transported fastened to the tail feathers of the pigeons. Upon receipt the microphotograph was reattached to a glass frame and was then projected by magic lantern on the wall. The message contained in the microfilm could then be transcribed or copied.Newsletter of the Illinois State Archives & The Illinois State Historical Records Advory Board Jesse White Secretary of State & State Archivist Volume 2 Number 1 Quote: "Despite Dancer's early work, in 1859, Ree Dagron, a French optician, received the first patent for microfilm. Using Dancer's techniques, Dagron manufactured and sold microphotograph trinkets. In 1870–71, during the Franco-Prussian War, Dagron demonstrated a practical use for microforms. During the siege of Paris, the French used carrier pigeons to transparrt microfilmed messages across German dices."The Focal Encyclopedia of Photography: Digital Imaging, Theory and Applications, History, and Science p. 94 By Michael R. Peres Contributor Michael R. Peres Published by Focal Press, 2007 By 28 January 1871, when Paris and the Government of National Defense surrendered, Dagron had delivered 115,000 messages to Paris by carrier pigeon.
The chemist Charles-Louis Barreswil proposed the application of photographic methods with prints of a reduced size. The prints were on photographic paper and did not exceed 40 mm, to permit insertion in a goose-quill or thin metal tube, which protected against the elements. The pigeons each carried a dispatch that was tightly rolled and tied with a thread, and then attached to a tail feather of the pigeon. The dispatch was protected by being inserted in the quill, which was then attached to the tail feather.
The developments in microphotography continued through the next decades, but it was not until the turn of the century that its potential for practical usage was applied more broadly. In 1896, Canadian engineer Reginald A. Fessenden suggested microforms were a compact solution to engineers' unwieldy but frequently consulted materials. He proposed that up to 150,000,000 words could be made to fit in a square inch, and that a one-foot cube could contain 1.5 million volumes.