What is Microfilm?
Managing input for microfilm systems
Input is likely to come from many sources and in many formats. Different methods may be required for each source, but in most systems the bulk of the input will arrive on paper or in digital format. Documents on paper are said to be in analogue (human readable) format and they remain in that format after filming although they need enlargement before they can be read. Input in digital (computer readable) format needs conversion to analogue before it can be filmed and this takes place in a COM recorder which is sometimes called an archiver. Basically these units display images on a CRT and film the display or “write” on to the film using a laser.
Paper often requires preparation prior to input which may involve the removal of staples, unbinding and sorting into document types or sizes. Some rotary cameras with automatic feeders will accept mixed input, but most will be unable to detect the start and end of a batch of documents without some form of mark or header sheet. Occasional double sided documents can present problems but, if the majority of input is double sided, duplex cameras are available which automatically scan both sides in one pass. The majority of rotary cameras are limited to A4 or A3 input. Input up to A0 size or above is usually filmed on planetary cameras and they are also employed for rare and delicate input. Bound books must be filmed on flat-bed units which often incorporate a book cradle to keep the adjoining pages of bound books in the same plane. This is labour intensive and can be a slow process compared with rotary filming.
Film scanning generates a raster bit-map of the document. The process is similar to fax in that a sensor passes over a small section of the document and detects the presence or absence of a mark at closely spaced points, the document or the scanning head is advanced and another line is scanned until the task is completed. For most applications a raster of 200 points per inch is sufficient. Compression techniques reduce the amount of data to be stored but an A4 size 200 dpi greyscale image can require 1.2 Mb. Higher resolution scans and colour scans generate much higher volumes. An exact facsimile of any scanned and stored image can be re-created for display, transmission or printout and it can usually be re-sized or annotated but not edited or otherwise altered.
When extensive search facilities are not required and the document can be retrieved via a few fixed fields only the raster image need be stored but relevant retrieval data will still have to be added to an index. This can sometimes be done during the quality control process subsequent to filming. The images are presented to an operator on a screen which also contains a form on which blank fields must be completed. These methods allow images to be stored and retrieved and there is usually provision for annotation but it is not normally possible to edit or revise any image. This can be a significant advantage if it might be required as evidence.
Filming and scanning services
Facilities typically offered by document scanning bureaux often include microfilming and film duplication, film scanning and digitising but some may only be able to cater for small volumes while others may not be equipped to handle all film formats. Some bureaux can also hold very large volumes of film or digital records in a secure archive to which clients have on-line or web access. Many bureaux stock fast-moving consumables such as film, magnetic and optical media, toner and print paper and they may also have local sales agencies for hardware such as readers, scanners, printers, and monitors.
There is a sound case for film being employed as a back-up to any electronic archive. This reflects growing concern that rapid advances in computing technology may necessitate the frequent conversion of archives held in outdated formats or on magnetic media for which reading equipment is no longer supported. Scanner/cameras create a record on roll film in addition to digitised output. This provides a security backup and permits destruction of the original paper as the film is ideal for archival storage and fully acceptable as evidence if correctly produced. These units are essentially a combination of a document scanner and a microfilm camera. Models are available for typical office documents and large formats such as maps. plans and drawings, and cameras are offered for roll and fiche. The process produces a film image for archival storage as a true record of each document and a digital file for input to an electronic document management system.
Input from microfilm
Some companies already have large collections of information on microforms which they would like to access via an electronic document management system. Careful consideration is essential before deciding to scan the entire content because, if references are likely to be relatively infrequent, it may be preferable to buy an inexpensive reader-scanner and scan specific images only when they are needed rather than pay for the conversion and indexing of the entire film archive.
Images on microforms are input on special scanners which are often dedicated to one film format. The data sheets for film scanners on this site are split into four groups, those for aperture cards,models designed for microfiche and jackets, models for roll formats and those for multiple formats.
Aperture card scanners
Digital scanners for aperture cards can usually optically enlarge film images on to an integral screen for reference or verification but some are specifically designed to scan the film images for input to a CAD system, printout via a laser-printer or plotter or store them to disk. Some models can accept more than one film format and they will be found under Film scanners – universal on this site. Factors such as the choice of lenses, film carrier options and the image retrieval methods available are similar to optical readers and reader-printers, but a much wider range of printout is available via a laser-printer. Options typically include the ability to mask any part of the image, enhance the quality of images, correct skewed images, and electronically vary enlargement or printout.
Production scanners for aperture cards are intended for the rapid digitising of high volumes of data from film rather than reference to or enlargement from selected images. A screen may be provided for verification purposes, but if a facility for full size display is required it is usually provided via a CRT monitor in order to show the quality of the digitised data rather than an optical enlargement of the microfilm image. Aperture card scanners can be hopper-fed to operate automatically and most aperture card scanners can interpret Hollerith code, text, or marks on the cards to compile indexing data during the scanning operation.
Scanners for fiche and jackets
Inexpensive fiche scanners are available to digitise selected frames from fiche and jackets but this is a relatively slow process. Production scanners for fiche are intended for the rapid digitising of high volumes of data from fiche. If a facility for full size display is required it is usually provided via a CRT monitor rather than an optical enlargement of the microfilm image. It is important to ensure that a high speed fiche scanner can cater for the particular grid layout of the input. Jackets are less suitable for automated scanning because the image layout is not precise, but some film scanners can compensate automatically for irregularities in format and may even accept mixed image sizes such as 35mm and 16mm.
Applications include file conversion of microfiche and jacket archives to electronic document management systems. Production scanners for high volumes are fast and relatively expensive. It is necessary to have a long-term requirement for the scanning of high volumes of input to justify an in-house unit, but many microfilm bureaux now offer fiche scanning services at competitive prices.
Scanners for roll film formats
For occasional use and low volume applications digital reader-scanners are available which optically enlarge film images on to an integral screen for reference or verification but also incorporate a facility to scan the images for input to an electronic document management system, printout via a laser-printer or store them to disk. Digital reader-printers have their own section under micrographic equipment. Most scanners for roll film are intended for the rapid digitising of high volumes of data from film rather than reference to or enlargement from specific images. Roll formats can be scanned automatically; the scanner advances the film from frame to frame by detecting image blips or inter-frame gaps. A screen may be provided for verification purposes, but if a facility for full size display is required it is usually provided via a CRT monitor.
Uses include file conversion of microfilm archives to electronic document management systems and the automation of document scanning when assorted input is involved. If documents of different sizes and quality are to be input to an electronic document management system it may not be possible to batch scan and input may be very slow. An alternative input method, often advocated for maps, drawings and other large originals, is to microfilm the paper documents to create an archival film record, then scan the film rather than the original paper. If roll film is employed the scanning operation can then be performed automatically at high speed. This avoids the need for large format document scanners which tend to be slow and expensive and also overcomes any problems with bound or delicate input. It also results in a permanent film record of the content at the time of filming.
Production film scanners are fast and relatively expensive. It is necessary to have a long-term requirement for the scanning of fairly high volumes of input to justify an in-house unit, but many microfilm bureaux now offer film scanning services at prices which make even low-volume input economic.
Universal film scanners
Low volume digital reader-scanners can usually optically enlarge film images on to an integral screen for reference or verification but they may also incorporate a facility to scan the images for input to an electronic document management system, printout via a laser-printer or store them to disk. Versions are available to accept all microforms but this may involve changing film carriers and motorised roll film carriers can be heavy. Factors such as the choice of lenses, film carrier options and the image retrieval methods available are similar to optical readers and reader-printers, but a much wider range of printout is available via a laser-printer. Options typically include the ability to mask any part of the image, correction of skewed images, superimposition of repetitive data on prints and electronically variable enlargement.
High volume universal scanners for roll film, fiche and aperture cards are intended for the rapid digitising of high volumes of data from film rather than reference to or enlargement from specific images. As with slower units, film carriers usually have to be interchanged between roll and flat formats.
This can come from internal sources, such as data processing, word processing, drawing office CAD systems, etc. If the software on which it is generated is interfaced with the document management system it can be converted to film as received. Digital input from external sources may come in a wide variety of formats, some of which may have to be converted. Input from the web can also be accepted by some COM facilities. In most cases this data is already indexed and the index can be incorporated into an EDM System.
Maintenance manuals, catalogues, software and similar publications can be distributed to agents and customers who are not connected to the network by printing out to microfiche. These incorporate indexes, so they are completely self-contained. Once very popular for maintenance manuals and price lists, these applications have largely been overtaken by distribution on CDs or on line access.
COM recording and plotting to film
When documents need to be available for instant access it is logical to hold them in digital format within electronic document management systems, but the period of peak activity is usually of relatively short duration. Thereafter the need for retrieval remains a possibility, but in many applications the majority of the documents will never be referenced again.
Despite advances in the capacity of digital storage, it is often impractical to hold archival information indefinitely on instant access devices. Another problem is that as systems evolve it is time-consuming and expensive to ensure that all digital archives held on outdated media or in abandoned formats are converted to the new format or operating system. Repetitive conversion also carries an attendant risk of data loss. The need to cater for large quantities of archival material can act as a brake on system development.
Converting archival digital data to microfilm creates a secure storage solution which is fully standardised and which will permit access in 100 or more years time, no matter how much the digital system may have changed in that period.
COM (Computer Output Microfilm, also known as film archiving) offers a fast and economical method of converting digital files to proven and archival microformats. The master films should be preserved in a remote archive, but exact copies can be produced inexpensively for distribution or use when access from digital storage is terminated.
If a microfilmed document, thought to be archival, needs to be re-input to an electronic document management system, it can easily be scanned and digitised. Reader-scanners suitable for such applications can also produce prints via a laser-printer if hard copy is preferable. They are listed on this site under Film Scanners.
COM recorders can now emulate sophisticated laser-printers to allow information on film to be recorded exactly as if the information had been printed to paper and then microfilmed. Raster data derived from document scanning can also be directly input to several models. Speeds are impressive and some machines can convert a print stream to images on roll film or microfiche at up to 400 pages per minute. Common reduction ratios are 24X, 42X, 48X and 72X.
Systems involving the distribution of copy films to outstations, and many internal office applications, tend to employ microfiche but 16mm roll is widely used, especially for archiving applications. COM output on 16mm roll is usually in the form of blipped images so that the film can be used in conjunction with automated image retrieval systems. When microfiche are employed, the entire process of recording, film development, duplication and collation of variable numbers of copies from each master fiche can be conducted as an automated in-line operation.
COM recorders can operate as on-line or off-line devices. This permits data held on a wide variety of storage media to be converted by a bureau facility and returned as fully indexed microfilm. One relatively low-priced COM recorder has been designed for in-house applications requiring substantial volumes of digital data to be archived on 16mm roll film. Images are accepted in TIFF, JPEG and other raster formats and written to film at up to 240 letter-sized images per minute. The unit appears as a drive to the system. It handles image resolutions up to 600 dpi and scales images automatically from 20:1 to 60:1 reduction to match the application specification.
35mm roll and aperture card COM output options are also available and these typically relate to the plotting of CAD output direct to microfilm. The 35mm frames may be set sequentially along a roll or recorded directly on to single 35mm frames mounted in aperture cards. When aperture cards are employed, the unit normally contains its own film processor in order to deliver fully processed and titled aperture cards at speeds of up to 35 cards per hour. Hollerith punching of the cards is also possible during the production process. Resolution can be equal to 400 dpi on the original size drawing.