Microform - AbsoluteAstronomy.com

Microforms are any forms, either films

Photographic film

Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

or paper, containing microreproductions of documents for transmission, storage, reading, and printing. Microform images are commonly reduced to about one twenty-fifth of the original document size. For special purposes, greater optical reductions may be used.

All microform images may be provided as positives or negatives, more often the latter.

Three formats are common: microfilm (reels), aperture card
Aperture card
An aperture card is a type of punched card with a cut-out window into which a chip of microfilm is mounted. Such a card is used for archiving or for making multiple inexpensive copies of a document for ease of distribution...

s and microfiche (flat sheets). Microcards, a format no longer produced, were similar to microfiche, but printed on cardboard rather than photographic film.

History

Using the daguerreotype

Daguerreotype

The daguerreotype was the first commercially successful photographic process. The image is a direct positive made in the camera on a silvered copper plate....

process, John Benjamin Dancer

John Benjamin Dancer

John Benjamin Dancer was a scientific instrument maker and inventor of microphotography. He also pioneered stereography. By 1835, he controlled his father's instrument making business. He was responsible for various inventions, but did not patent many of his ideas. In 1852, he invented the...

was one of the first to produce micro-photographs, in 1839. He achieved a reduction ratio of 160:1. Dancer perfected his reduction procedures with Frederick Scott Archer

Frederick Scott Archer

Frederick Scott Archer invented the photographic collodion process which preceded the modern gelatin emulsion. He was born in Bishop's Stortford in the UK and is remembered mainly for this single achievement which greatly increased the accessibility of photography for the general public.tyler was...

’s wet collodion process

Collodion process

The collodion process is an early photographic process. It was introduced in the 1850s and by the end of that decade it had almost entirely replaced the first practical photographic process, the daguerreotype. During the 1880s the collodion process, in turn, was largely replaced by gelatin dry...

, developed in 1850–51, but he dismissed his decades-long work on micro-photographs 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 by the 1858 Dictionary of Photography, which called the process “somewhat trifling and childish.”

Microphotography was first suggested as a document preservation method in 1851 by James Glaisher

James Glaisher

James Glaisher FRS , was an English meteorologist and aeronaut.Born in Rotherhithe, the son of a London watchmaker, Glaisher was a Junior assistant at the Cambridge Observatory from 1833 to 1835 before moving to the Royal Greenwich Observatories, where he served as Superintendent of the Department...

, an astronomer, and in 1853 by John Herschel

John Herschel

Sir John Frederick William Herschel, 1st Baronet KH, FRS ,was an English mathematician, astronomer, chemist, and experimental photographer/inventor, who in some years also did valuable botanical work...

. Both men attended the 1851 Great Exhibition

The Great Exhibition

The Great Exhibition of the Works of Industry of all Nations or The Great Exhibition, sometimes referred to as the Crystal Palace Exhibition in reference to the temporary structure in which it was held, was an international exhibition that took place in Hyde Park, London, from 1 May to 15 October...

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.

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 seized by a wider audience. 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.

In 1906, Paul Otlet

Paul Otlet

Paul Marie Ghislain Otlet was an author, entrepreneur, visionary, lawyer and peace activist; he is one of several people who have been considered the father of information science, a field he called "documentation". Otlet created the Universal Decimal Classification, one of the most prominent...

and Robert Goldschmidt proposed the livre microphotographique as a way to alleviate the cost and space limitations imposed by the codex

Codex

A codex is a book in the format used for modern books, with multiple quires or gatherings typically bound together and given a cover.Developed by the Romans from wooden writing tablets, its gradual replacement...

format. Otlet’s overarching goal was to create a World Center Library of Juridical, Social and Cultural Documentation, and he saw microfiche as way to offer a stable and durable format that was inexpensive, easy to use, easy to reproduce, and extremely compact. In 1925, the team spoke of a massive library where each volume existed as master negatives and positives, and where items were printed on demand for interested patrons.

In the decade of the 1920s microfilm began to be used in a commercial setting. New York City banker George McCarthy was issued a patent in 1925 for his "Checkograph" machine, designed to make micrographic copies of cancelled checks for permanent storage by financial institutions. In 1928, the Eastman Kodak Company bought McCarthy's invention and began marketing check microfilming devices under its "Recordak" division.

Between 1927 and 1935, the Library of Congress

Library of Congress

The Library of Congress is the research library of the United States Congress, de facto national library of the United States, and the oldest federal cultural institution in the United States. Located in three buildings in Washington, D.C., it is the largest library in the world by shelf space and...

microfilmed more than three million pages of books and manuscripts in the British Library

British Library

The British Library is the national library of the United Kingdom, and is the world's largest library in terms of total number of items. The library is a major research library, holding over 150 million items from every country in the world, in virtually all known languages and in many formats,...

; in 1929 the Social Science Research Council

Social Science Research Council

The Social Science Research Council is a U.S.-based independent nonprofit organization dedicated to advancing research in the social sciences and related disciplines...

and the American Council of Learned Societies

American Council of Learned Societies

The American Council of Learned Societies , founded in 1919, is a private nonprofit federation of seventy scholarly organizations.ACLS is best known as a funder of humanities research through fellowships and grants awards. ACLS Fellowships are designed to permit scholars holding the Ph.D...

joined to create a Joint Committee on Materials Research, which looked closely at microform’s potential to serve small print runs of academic or technical materials; in 1933, Charles C. Peters developed a method to microformat dissertations; in 1934 the United States National Agriculture Library implemented the first microform print-on-demand service, which was quickly followed by a similar commercial concern, Science Service.

In 1935, Kodak's Recordak division began filming and publishing The New York Times
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...

on reels of 35 millimeter microfilm, ushering in the era of newspaper

Newspaper

A newspaper is a scheduled publication containing news of current events, informative articles, diverse features and advertising. It usually is printed on relatively inexpensive, low-grade paper such as newsprint. By 2007, there were 6580 daily newspapers in the world selling 395 million copies a...

preservation on film. This method of information storage received the sanction of the American Library Association

American Library Association

The American Library Association is a non-profit organization based in the United States that promotes libraries and library education internationally. It is the oldest and largest library association in the world, with more than 62,000 members....

at it annual meeting in 1936, when it officially endorsed microforms.

Harvard University Library

Harvard University Library

The Harvard University Library system comprises about 90 libraries, with more than 16 million volumes. It is the oldest library system in the United States, the largest academic and the largest private library system in the world...

was the first major institution to realize the potential of microfilm to preserved broadsheet

Broadsheet

Broadsheet is the largest of the various newspaper formats and is characterized by long vertical pages . The term derives from types of popular prints usually just of a single sheet, sold on the streets and containing various types of material, from ballads to political satire. The first broadsheet...

s printed on high-acid newsprint and it launched its "Foreign Newspaper Project" to preserve such ephemeral publications in 1938. Roll microfilm proved far more satisfactory as a storage medium than earlier methods of film information storage, such as the Photoscope, the Film-O-Graph, the Fiske-O-Scope, and filmslides.

The year 1938 also saw another major event in the history of microfilm when University Microfilms International

University Microfilms International

University Microfilms International or UMI, was founded in the 1930s by Eugene Power in Ann Arbor. By June 1938, Power worked in two rented rooms from a downtown Ann Arbor funeral parlor, specializing in microphotography to preserve library collections...

(UMI) was established by Eugene Power. For the next half century, UMI would dominate the field, filming and distributing microfilm editions of current and past publications and academic dissertations. After another short-lived name change, UMI was made a part of ProQuest Information and Learning

ProQuest

ProQuest LLC is an Ann Arbor, Michigan-based electronic publisher and microfilm publisher.It provides archives of sources such as newspapers, periodicals, dissertations, and aggregated databases of many types. Its content is estimated at 125 billion digital pages...

in 2001.

Uses

Systems that mount microfilm images in punched card

Punched card

A punched card, punch card, IBM card, or Hollerith card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions...

s have been widely used for archival storage of engineering information.

For example, when airline

Airline

An airline provides air transport services for traveling passengers and freight. Airlines lease or own their aircraft with which to supply these services and may form partnerships or alliances with other airlines for mutual benefit...

s demand archival engineering drawings to support purchased equipment (in case the vendor goes out of business, for example), they normally specified punch-card-mounted microfilm with an industry-standard indexing system punched into the card. This permits automated reproduction, as well as permitting mechanical card-sorting equipment to sort and select microfilm drawings.

Aperture card mounted microfilm is roughly 3% of the size and space of conventional paper or vellum engineering drawings. Some military contracts around 1980 began to specify digital storage of engineering and maintenance data because the expenses were even lower than microfilm, but these programs are now finding it difficult to purchase new readers for the old formats.

Microfilm first saw military use during the Franco-Prussian War

Franco-Prussian War

The Franco-Prussian War or Franco-German War, often referred to in France as the 1870 War was a conflict between the Second French Empire and the Kingdom of Prussia. Prussia was aided by the North German Confederation, of which it was a member, and the South German states of Baden, Württemberg and...

of 1870–71. During the Siege of Paris

Siege of Paris

The Siege of Paris, lasting from September 19, 1870 – January 28, 1871, and the consequent capture of the city by Prussian forces led to French defeat in the Franco-Prussian War and the establishment of the German Empire as well as the Paris Commune....

, the only way for the provincial government in Tours

Tours

Tours is a city in central France, the capital of the Indre-et-Loire department.It is located on the lower reaches of the river Loire, between Orléans and the Atlantic coast. Touraine, the region around Tours, is known for its wines, the alleged perfection of its local spoken French, and for the...

to communicate with Paris was by pigeon post

Pigeon post

Pigeon post is the use of homing pigeons to carry messages. Pigeons were effective as messengers due to their natural homing abilities. The pigeons were transported to a destination in cages, where they would be attached with messages, then naturally the pigeon would fly back to its home where the...

. As the pigeons could not carry paper dispatches, the Tours government turned to microfilm. Using a microphotography unit evacuated from Paris

Paris

Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

before the siege, clerks in Tours photographed paper dispatches and compressed them to microfilm, which were carried by homing pigeons into Paris and projected by magic lantern

Magic lantern

The magic lantern or Laterna Magica is an early type of image projector developed in the 17th century.-Operation:The magic lantern has a concave mirror in front of a light source that gathers light and projects it through a slide with an image scanned onto it. The light rays cross an aperture , and...

while clerks copied the dispatches onto paper.

Additionally, the US Victory Mail

V-mail

V-mail, short for Victory Mail, is a hybrid mail process used during the Second World War in America as the primary and secure method to correspond with soldiers stationed abroad...

, and the British "Airgraph" system it was based on, were used for delivering mail between those at home and troops serving overseas during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. The systems worked by photographing large amounts of censored mail

Postal censorship

Postal censorship is the inspection or examination of mail, most often by governments. It can include opening, reading and total or selective obliteration of letters and their contents, as well as covers, postcards, parcels and other postal packets. Postal censorship takes place primarily but not...

reduced to thumb-nail size onto reels of microfilm, which weighed much less than the originals would have. The film reels were shipped by priority air freight to and from the home fronts, sent to their prescribed destinations for enlarging at receiving stations near the recipients, and printed out on lightweight photo paper. These facsimiles of the letter-sheets

Letter sheet

In philatelic terminology a Letter sheet, often written lettersheet, is nowadays an item of postal stationery issued by a postal authority. It is a sheet of paper that can be folded, usually sealed , and mailed without the use of an envelope...

were reproduced about one-quarter the original size and the miniature mails were then delivered to the addressee. Use of these microfilm systems saved significant volumes of cargo capacity needed for vital war supplies. An additional benefit was that the small, light weight reels of microfilm were almost always transported by air, and as such were much quicker than any surface mail

Mail

Mail, or post, is a system for transporting letters and other tangible objects: written documents, typically enclosed in envelopes, and also small packages are delivered to destinations around the world. Anything sent through the postal system is called mail or post.In principle, a postal service...

services.

Libraries began using microfilm in the mid-20th century as a preservation strategy for deteriorating newspaper collections. Books and newspapers that were deemed in danger of decay could be preserved on film and thus access and use could be increased. Microfilming was also a space-saving measure. In his 1945 book, “The Scholar and the Future of the Research Library,” Fremont Rider

Fremont Rider

Arthur Fremont Rider was an American writer, poet, editor, inventor, genealogist, and librarian. He studied under Melvil Dewey, of whom he wrote a biography for the ALA. Throughout his life he wrote in several genres including plays, poetry, short stories, non-fiction and an auto-biography which...

calculated that research libraries were doubling in space every sixteen years. His suggested solution was microfilming, specifically with his invention, the microcard. Once items were put onto film, they could be removed from circulation and additional shelf space would be made available for rapidly expanding collections. The microcard was superseded by microfiche. By the 1960s, microfilming had become standard policy.

Visa and National City

National City

-Places in the United States of America:*National City, California*National City, Illinois*National City, Michigan*National City, Nevada, a ghost town now known as Bristol Wells-Banks:...

use microfilm( roll microfilm and fiche) to store bank statements, financial records storage, personal records storage, records management storage, legal records storage, and produce microfilm, from digital records, that is placed into storage.

The 2011 UK census

Census

A census is the procedure of systematically acquiring and recording information about the members of a given population. It is a regularly occurring and official count of a particular population. The term is used mostly in connection with national population and housing censuses; other common...

data will be stored on microfilms due to lack of storage space.

Advantages

The medium has numerous advantages:

It enables libraries to greatly expand access to collections without putting rare, fragile, or valuable items at risk of theft or damage.
It is compact, with far smaller storage costs than paper documents. Normally 98 document size pages fit on one fiche, reducing to about 0.25% original material. When compared to filing paper, microforms can reduce space storage requirements by up to 95%.
It is cheaper to distribute than paper copy. Most microfiche services get a bulk discount on reproduction rights, and have lower reproduction and carriage costs than a comparable amount of printed paper.
It is a stable archival form when properly processed and stored. Preservation standard microfilms use the silver halide
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...

process, creating silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

images in hard gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...

emulsion on a polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

base. With appropriate storage conditions, this film has a life expectancy of 500 years. Unfortunately, in tropical climates with high humidity, fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

eats the gelatin used to bind the silver halide. Thus, diazo
Diazo
Diazo refers to a type of organic compound called diazo compound that has two linked nitrogen atoms as a terminal functional group. The general formula is R2C=N2. The simplest example of a diazo compound is diazomethane...

-based systems with lower archival lives (20 years) which have polyester or epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....

surfaces are used.
Since it is analog (an actual image of the original data), it is easy to view. Unlike digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

media, the format requires no software to decode the data stored thereon. It is instantly comprehensible to persons literate in the language; the only equipment that is needed is a simple magnifying glass. This eliminates the problem of software obsolescence.
It is virtually impossible to mutilate. Users cannot tear pages from or deface microforms.
It has low intrinsic value and does not attract thieves. Few heavily-used microform collections suffer any losses due to theft.
Prints from microfilm are accepted in legal proceedings as substitutes for original documents.

Disadvantages

The principal disadvantage of microforms is that the image is (usually) too small to read with the naked eye. Libraries must use either special readers that project full-size images on a ground-glass or frosted acrylic screen or a modern Viewer/Scanner which converts the image from analog to digital -see section below on Digital Conversion.
Reader machines used to view microfilm are often difficult to use, requiring users to carefully wind and rewind until they have arrived at the point where the data they are looking for is stored.
Photographic illustrations reproduce poorly in microform format, with loss of clarity and halftones. However the latest electronic digital viewer/scanners have the ability to scan in gray shade which greatly increases the quality of photographs, but they still can not duplicate the nuances of true gray shade photographs -due to the inherent bi-tonal nature of microfilm.
Reader-printers are not always available, limiting the user's ability to make copies for their own purposes. Conventional photocopy machines cannot be used.
Color microform is extremely expensive, thus discouraging most libraries supplying color films. Color photographic dyes also tend to degrade over the long term. This results in the loss of information, as color materials are usually photographed using black and white film.
When stored in the highest-density drawers, it is easy to misfile a fiche, which is thereafter unavailable. As a result, some libraries store microfiche in a restricted area and retrieve it on demand. Some fiche services use lower-density drawers with labeled pockets for each card.
Like all analog media formats, microfiche is lacking in features enjoyed by users of digital media. Analog copies degrade with each generation, while digital copies have much higher copying fidelity. Digital data can also be indexed and searched easily.
Reading microfilms on a machine for some time may cause headache and/or eyestrain.

Readers and printers

Desktop readers are boxes with a translucent screen at the front on to which is projected an image from a microform. They have suitable fittings for whatever microform is in use. They may offer a choice of magnifications. They usually have motors to advance and rewind film. When coding blips are recorded on the film a reader is used that can read the blips to find any required image.

Portable readers are plastic devices that fold for carrying; when open they project an image from microfiche on to a reflective screen. For example, with M. de Saint Rat, Atherton Seidell

Atherton Seidell

Atherton Seidell , a founder of the American Documentation Institute , was a chemist and who became a strong proponent of the use of microfilm for the management of scientific information...

developed a simple, inexpensive ($2.00 in 1950), monocular microfilm viewing device, known as the "Seidell viewer," that was sold during the 1940s and 1950s.

A microfilm printer contains a xerographic copying process, like a photocopier

Photocopier

A photocopier is a machine that makes paper copies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xerography, a dry process using heat...

. The image to be printed is projected with synchronised movement on to the drum. These devices offer either small image preview for the operator or full size image preview, when it is called a reader printer. Microform printers can accept positive or negative films and positive or negative images on paper. New machines allow the user to scan a microform image and save it as a digital file -see the section below on Digital conversion.

Media

Flat film : 105 x 148 mm flat film is used for micro images 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 2.00 x 2.80 metres, that is 79 x 110 in. These films are stored as microfiche.

Microfilm : 16 mm

16 mm film

16 mm film refers to a popular, economical gauge of film used for motion pictures and non-theatrical film making. 16 mm refers to the width of the film...

or 35 mm film

35 mm film

35 mm film is the film gauge most commonly used for chemical still photography and motion pictures. The name of the gauge refers to the width of the photographic film, which consists of strips 35 millimeters in width...

to motion picture standard is used, usually unperforated. Roll microfilm is stored on open reels or put into cassettes. The standard lengths for using roll film is 30.48 m (100 ft)for 35mm rolls, and 100 ft, 130 ft and 215 feet for 16mm 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 micro images 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 card

Aperture card

An aperture card is a type of punched card with a cut-out window into which a chip of microfilm is mounted. Such a card is used for archiving or for making multiple inexpensive copies of a document for ease of distribution...

s are Hollerith cards into which a hole has been cut. A 35 mm microfilm chip is mounted in the hole inside of a clear plastic sleeve, or secured over the aperture by an adhesive tape. They are used for engineering drawings, for 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.

Microfiche : A microfiche is a flat film 105 x 148 mm in size, that is ISO A6

ISO 216

ISO 216 specifies international standard paper sizes used in most countries in the world today. It defines the "A" and "B" series of paper sizes, including A4, the most commonly available size...

. It carries a matrix of micro images. All microfiche are read with text parallel to the long side of the fiche. Frames may be landscape or portrait. Along the top of the fiche a title may be recorded for visual identification. The most commonly used format is a portrait image of about 10 x 14 mm. Office size papers or magazine pages require a reduction of 24 or 25. Microfiche are stored in open top envelopes which are put in drawers or boxes as file cards, or fitted into pockets in purpose made books.

Ultrafiche : (also 'ultramicrofiche') is an exceptionally compact version of a microfiche or microfilm, storing analog data at much higher densities. Ultrafiche can be created directly from computers using appropriate peripherals. They are typically used for storing data gathered from extremely data-intensive operations such as remote sensing.

Image creation

To create microform media, a planetary camera

Camera

A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...

is mounted with the vertical axis above a copy that is stationary during exposure. High volume output is possible with a rotary camera which moves the copy smoothly through the camera to expose film which moves with the reduced image. Alternatively, it may be produced by computers, i.e. COM (computer output microfilm).

Film

Normally microfilming uses high resolution panchromatic

Panchromatic

Panchromatic film is a type of black-and-white photographic film that is sensitive to all wavelengths of visible light. A panchromatic film therefore produces a realistic reproduction of a scene as it appears to the human eye. Almost all modern photographic film is panchromatic, but some types are...

monochrome stock. Positive color film giving good reproduction and high resolution can also be used. Roll film is provided 16, 35 and 105 mm wide in lengths of 30 metres (100 ft) and longer, and is usually unperforated. Roll film is developed, fixed and washed by continuous processors.

Sheet film is supplied in ISO A6 size. This is either processed by hand or using a dental X-ray processor. Camera film is supplied ready mounted in aperture cards. Aperture cards are developed, fixed and washed immediately after exposure by equipment fitted to the camera.

Early cut sheet microforms and microfilms (to the 1930s) were printed on nitrate film, which poses high risks to their holding institutions, as nitrate film is explosive and flammable. From the late 1930s to the 1980s, microfilms were usually printed on a cellulose acetate

Cellulose acetate

Cellulose acetate , first prepared in 1865, is the acetate ester of cellulose. Cellulose acetate is used as a film base in photography, as a component in some adhesives, and as a frame material for eyeglasses; it is also used as a synthetic fiber and in the manufacture of cigarette filters and...

base, which is prone to tears, vinegar syndrome, and redox blemishes. Vinegar syndrome is the result of chemical decay and produces "buckling and shrinking, embrittlement, and bubbling". Redox blemishes are yellow, orange or red spots 15–150 micrometres in diameter created by oxidative attacks on the film, and are largely due to poor storage conditions.

Cameras

Flat film
The simplest microfilm camera that is still in use is a rail mounted structure at the top of which is a bellows camera for 105 x 148 mm film. A frame or copy board holds the original drawing vertical. The camera has a horizontal axis which passes through the center of the copy. The structure may be moved horizontally on rails.

In a darkroom

Darkroom

A darkroom is a room that can be made completely dark to allow the processing of light sensitive photographic materials, including photographic film and photographic paper. Darkrooms have been created and used since the inception of photography in the early 19th century...

a single film may be inserted into a dark slide or the camera may be fitted with a roll film holder which after an exposure advances the film into a box and cuts the frame off the roll for processing as a single film.

Roll film
For engineering drawings a freestanding open steel structure is often provided. A camera may be moved vertically on a track. Drawings are placed on a large table for filming, with centres under the lens. Fixed lights illuminate the copy. These cameras are often over 4 metres (10 feet) high. These cameras accept roll film stock of 35 or 16 mm.

For office documents a similar design may be used but bench standing. This is a smaller version of the camera described above. These are provided either with the choice of 16 or 35 mm film or accepting 16 mm film only. Non adjustable versions of the office camera are provided. These have a rigid frame or an enveloping box that holds a camera at a fixed position over a copy board. If this is to work at more than one reduction ratio there are a choice of lenses.

Some cameras expose a pattern of light, referred to as blips, to digitally identify each adjacent frame. This pattern is copied whenever the film is copied for searching.

Flow roll film cameras
A camera is built into a box. In some versions this is for bench top use, other versions are portable. The operator maintains a stack of material to be filmed in a tray, the camera automatically takes one document after another for advancement through the machine. The camera lens sees the documents as they pass a slot. Film behind the lens advances exactly with the image.

Special purpose flow cameras film both sides of documents, putting both images side by side on 16 mm film. These cameras are used to record cheques and betting slips.

Microfiche camera
All microfiche cameras are planetary with a step and repeat mechanism to advance the film after each exposure. The simpler versions use a dark slide loaded by the operator in a dark room; after exposure the film is individually processed, which may be by hand or using a dental X-ray processor. Cameras for high output are loaded with a roll of 105 mm film. The exposed film is developed as a roll; this is sometimes cut to individual fiche after processing or kept in roll form for duplication.

Computer Output Microfilm

Equipment is available that accepts a data stream from a mainframe computer. This exposes film to produce images as if the stream had been sent to a line printer and the listing had been microfilmed. Because of the source one run may represent many thousands of pages.

Within the equipment character images are made by a light source; this is the negative of text on paper. COM is sometimes processed normally. Other applications require that image appears as a conventional negative; the film is then reversal processed. This outputs either 16 mm film or fiche pages on a 105 mm roll.

Because listing characters are a simple design, a reduction ratio of 50 gives good quality and puts about 300 pages on a microfiche. A microfilm plotter, sometimes called an aperture card plotter, accepts a stream that might be sent to a computer pen plotter. It produces corresponding frames of microfilm. These produce microfilm as 35 or 16 mm film or aperture cards.

Duplication

All regular microfilm copying involves contact exposure under pressure. Then the film is processed

Photographic processing

Photographic processing is the chemical means by which photographic film and paper is treated after photographic exposure to produce a negative or positive image...

to provide a permanent image. Hand copying of a single fiche or aperture card involves exposure

Contact print

A contact print is a photographic image produced from film; sometimes from a film negative, and sometimes from a film positive. The defining characteristic of a contact print is that the photographic result is made by exposing through the film negative or positive, onto a light sensitive material...

over a light box and then individually processing the film. Roll films are contact exposed via motor, either round a glass cylinder or through a vacuum, under a controlled light source. Processing may be in the same machine or separately.

Silver halide

Silver halide

A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...

film is a slow version of camera film with a robust top coat. It is suitable for prints or for use as an intermediate from which further prints may be produced. The result is a negative copy. Preservation standards require a master negative, a duplicate negative, and a service copy (positive). Master negatives are kept in deep storage, and duplicate negatives are used to create service copies, which are the copies available to researchers. This multi-generational structure ensures the preservation of the master negative.

Diazo-sensitised film for dye coupling in ammonia

Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

gives blue or black dye positive copies. The black image film can be used for further copying.

Vesicular film is sensitised with a diazo dye, which after exposure is developed by heat. Where light has come to the film remains clear, in the areas under the dark image the diazo compound is destroyed quickly, releasing millions of minute bubbles of nitrogen into the film. This produces an image that diffuses light. It produces a good black appearance in a reader, but it cannot be used for further copying.

Modern microfilming standards require that a master set of films be produced and set aside for safe storage, used only to make service copies. When service copies get lost or damaged, another set can be produced from the masters, thus reducing the image degradation that results from making copies of copies.

Format conversion

These conversions may be applied to camera output or to release copies. Single microfiche are cut from rolls of 105 mm film. A bench top device is available that enables an operator to cut exposed frames of roll film and fit these into ready made aperture cards.

Transparent jackets are made A5 size each with 6 pockets into which strips of 16 mm film may be inserted (or fewer pockets for 35 mm strips), so creating microfiche jackets or jacketed microfiche. Equipment allows an operator to insert strips from a roll of film. This is particularly useful as frames may be added to a fiche at any time. The pockets are made using a thin film so that duplicates may be made from the assembled fiche.

Digital conversion

Another type of conversion is microform to digital. This is done using an optical scanner

Image scanner

In computing, an image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop scanner where the document is placed on a glass...

that projects the film onto a CCD

Charge-coupled device

A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...

array and captures it in a raw digital format. Until recently, since the different types of microform are dissimilar in shape and size, the scanners were usually able to handle only one type of microform at a time. There are some scanners that have the possibility of swapping modules for the different microform types and the latest viewer/scanner can accept any microform (roll, fiche, opaque cards, fiche,and/or aperture cards). Software (normally on the scanner itself, but more recently in an attached PC) is then used to convert the raw capture into a standard image format for archival.

The physical condition of microfilm greatly impacts the quality of the digitized copy. Microfilm with a cellulose acetate base (popular through the 1970s) is frequently subject to vinegar syndrome, redox blemishes, and tears, and even preservation standard silver halide

Silver halide

film on a polyester

Polyester

Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

base can be subject to silvering and degradation of the emulsion—all issues which affect the quality of the scanned image.

Digitizing microfilm can be inexpensive when automated scanners are employed. The Utah Digital Newspapers Program has found that, with automated equipment, scanning can be performed at $0.15 per page. Recent additions to the digital scanner field have brought the cost of scanning down substantially so that when large projects are scanned (millions of pages) the price per scan can be pennies.

Modern microform scanners utilize 8 bit gray shade scanning arrays and are thus able to provide quite high quality scans in a wealth of different digital formats (CCITT Group IV which is compressed black & white -bitonal, JPG or JPEG which is gray or color compression, bitmaps which are not compressed, or a number of other (some proprietary) formats such as PDF, LZW, GIF, etc.). These modern scanners are also able to scan at "Archival" resolution up to 600 dpi.

For the resulting files to be useful, they must be organized in some way. This can be accomplished in a variety of different ways, dependent on the source media and the desired usage. In this regard, aperture cards with Hollerith information are probably the easiest since image data can be extracted from the card itself if the scanner supports it. Some types of microfilm will contain a counter next to the images, these can be referenced to an already existing database

Database

A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...

. Other microfilm reels will have a 'blip' system: small marks next to the images of varying lengths used to indicate document hierarchy (longest: root, long: branch, short: leaf). If the scanner is able to capture and process these then the image files can be arranged in the same manner. Optical character recognition (OCR) is also frequently employed to provide automated full-text searchable files. Common issues that affect the accuracy of OCR applied to scanned images of microfilm include unusual fonts, faded printing, shaded backgrounds, fragmented letters, skewed text, curved lines and bleed through on the originals. For film types with no distinguishing marks, or when OCR is impossible (handwriting, layout issues, degraded text), the data must be entered in manually; a very time consuming process.

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.