CPA Newsletter #58, Jul 1993

CPA Newsletter #58, Jul 1993

Commission on Preservation and Access

The Commission on Preservation and Access


July 1993

Number 58

Congressional Testimony Supports NEH Preservation Program

The need for continued support for preservation microfilming, together with new research into digital technologies, was at the forefront of testimony on appropriations for the National Endowment for the Humanities (NEH) presented by David H. Stam, University Librarian at Syracuse University, on May 12, 1993, before the Subcommittee on the Interior and Related Agencies.

Stam testified on behalf of the Association of Research Libraries, the National Humanities Alliance, and the Commission. The testimony stressed the importance of sustained funding for the NEH Division of Preservation and Access to maintain the momentum of its 20-year brittle books program:

When Congress funded the first year of this 20-year effort, it set in motion a dynamic process which has resulted in the preservation microfilming of approximately 500,000 titles during the past five years. This achievement is far greater than it might seem, for not only have the individual books been preserved for the individual institutions which owned them, but service copies can now be obtained at low cost by any other institutions which have brittle copies of the same titles, thus avoiding the higher initial costs of preservation. They are also easily accessible to any other libraries or users who have need for those titles. Thus the NEH grants to large research libraries have directly and indirectly benefited all of the nation’s libraries and their users.

Stam described how the NEH preservation program had “enabled the nation’s research libraries to play a collaborative role in bringing in smaller academic and public libraries, and other historical societies, archives, and museums into the national infrastructure for preservation and access.”

The testimony urged that $2.3 million be restored to the NEH budget to reflect the original sixth-year program target of $20.3 million for library and archival preservation programs and stated that funds are needed for further exploration of the preservation potential of digital technology:

There seems no doubt that digital technology has the potential to expand dramatically the rapid availability of information to users everywhere. We are confident that continued research in digital technology, under NEH’s sponsorship and leadership, will provide the catalyst for perfecting these new technologies in the ongoing process of preserving the nation’s heritage.

Universities of Connecticut, Pittsburgh, AAP Join Commission Sponsors

The Universities of Connecticut and Pittsburgh, and the Association of American Publishers have become Commission sponsors, raising the number of supporting institutions to 60. Sponsors consist of 23 public and 27 private educational institutions, as well as eight public, state, and federal libraries; one higher education coalition, and one professional association. This continuing support, along with funds from foundations, provides the Commission with the ability to sustain existing nationwide activities and to develop new priority areas. All sponsors receive expedited mailings of publications, newsletters, and other information. The Commission’s two preservation and access exhibits are made available to sponsors at no charge.

Archive Using Hybrid Technologies to Preserve Access to Photographs

The Basel (Switzerland) Mission Archive is conducting a pilot project to preserve and provide international access to a collection of 50,000 historical photographs taken in Ghana, Cameroon, South India, South China, and Indonesian Kalimantan from the 1840’s to 1945. The project is using a combination of new technologies. Photographs are re-photographed on high-density, long-lasting film and transferred from film into an electronic image bank. Because of the speed of technical development in the field, no decision has yet been made about the technology of the image bank to be used for international access.

In the first three years, the project has sorted and grouped all 50,000 images, created a basic catalog for 36,000 of them, and re-photographed and transferred 28,400 into an image data bank.

Re-photography has a key role in the project according to project personnel because “it is not only a practicable step towards the preservation of large numbers of images in the highest resolution possible, but also makes possible the mechanical transfer of the images into any image bank technology.”

The photographs document the mission’s considerable interest in the cultural environments where its missionaries have worked. Half of the photographs in the image bank date from before 1914. Project directors have stated that, “Our plans go beyond merely returning photographs as archival objects to the areas in which they were taken. Pictures offer a basis for inter-cultural conversation whose potentiality has been scarcely noticed hitherto, and which we would like to see explored….”

More information is available from: Basler Mission, Abt. Archiv/Photoprojekt, Missionsstrasse 21, CH-4003 Basel, Switzerland.

Inside: “Preservation Film: Platform for Digital Access”

Included in this newsletter is the report, Preservation Film: Platform for Digital Access Systems, one in a series exploring new technologies for preservation and access.

A Science-Standards Review
The Stability of Optical Disks

The transition from a primarily print-on-paper environment to one that involves digital and optical technologies is presenting new choices of format for archival storage and access. This review was prepared at the Commission’s request by Peter Z. Adelstein* to provide a scientific and standards perspective on the use of optical disks as a storage medium. It is one of a series of publications and reports from the Commission on the capabilities of digital and optical technology for the capture, storage, transmission, and distribution of preserved information. For other technical discussions on the use of microfilm and digital technologies for preservation and access, contact the Commission for a current publications list.

There has been tremendous progress in imaging science during the past decade as a result of the development and commercialization of optical disks. They have found applications in the scientific, business and consumer communities where they have very powerful advantages. Optical disks (including CDs) offer great compaction of information and are particularly well suited to easy retrieval and ready access. Being in a digital format, they allow ready transmission of information. Since optical disks can be optically read without contact, disk wear upon repeated use is not a problem. However, this does not mean that they can be expected to have a very extended life compared to other imaging materials. Unfortunately there have been some publications which are not clear on this subject and some which suggest that optical disks are the ideal archival media. It is the purpose of this article to address this specific application and put the archival use of optical disks into some perspective.

Optical Disks as an Archival Medium

When we talk of an archival medium, we are talking about long-term retention of information for more than just decades. Commercial and consumer applications frequently require a useful life expectancy of optical disks for periods ranging from 10-30 years. However, libraries and archives are interested in information preservation for hundreds of years. It is with this requirement that optical disks present some problems.

Before discussing optical disks, let us review the attributes of photographic materials for preservation storage. The use of photographic materials as an archival medium rests on three factors. (1) These materials have been in existence for a long time and a great deal is known about the stability of both the photographic image and the photographic paper, plastic or glass support. (2) National and international standards have been adopted giving specifications for photographic film and recommended practices for the storage conditions and storage enclosures for photographic materials. (3) And lastly, photographic images are human readable. At most they require a light source and a means of magnification, both being simple requirements in the advanced scientific societies of today.

  1. In comparison, optical disk technology is relatively new. Photographic materials have been around for over 100 years, optical disks for about 20. The stability of optical disks is obviously very dependent upon the characteristics of a particular product and the raw materials used, e.g., metal or plastic. The stability will vary from manufacturer to manufacturer and may even vary within a product type.
  2. While there have been some excellent studies done on the longevity of this material, these have not yet resulted in any national or international specifications. Likewise documents do not yet exist detailing storage conditions that represent industry consensus. These points will be discussed in more detail later in this report.
  3. It is the third factor which is particularly pertinent: Optical disks are not human readable, requiring a system that includes the storage medium, hardware and software for access. The latter two represent two potent problems.

Availability of hardware to read optical disks should not be a problem when we talk of decades. However, hardware availability one hundred years from now is much more problematic. Equipment will wear out with time and repair is not always possible. New equipment or replacement parts will only be available if a market exists. It is unlikely that the archival community alone will provide a viable market for the hardware manufacturer.

Of even greater concern than the wearing out of hardware components is hardware or format obsolescence. Optical disk technology is a rapidly changing field and new formats are continually being developed. This development will not stop as the scientific development community improves data compaction, easy access or hardware simplicity. Many consumers concerned with data acquisition, storage and manipulation faced similar problems with the obsolescence of equipment to read punch cards or play magnetic tape in a reel-to-reel format.

Currently, the only practical solutions to hardware deterioration or obsolescence are to reformat the archival files on a regular schedule or before they become obsolete, or to store duplicate hardware. Clearly, the new technological environment will require new ways of approaching these problems.

Permanence Standards of Optical Disks

Standards in the United States are published under the umbrella of the American National Standards Institute (ANSI) and are prepared by committees accredited by ANSI. The need for standards on the permanence of electronic imaging was recognized by ANSI in 1987 and in 1989 Subcommittee IT9-5 was formed with this objective. This Subcommittee is composed of representatives from manufacturers, government agencies and consumers. They have been meeting twice a year since that time. The first activity was to divide the Subcommittee into several task groups, each with a specific goal. These included a task group on definitions, on storage conditions, and on magnetic tape specifications.

One task group is concerned with writing a test method which will predict the life expectancy of CDs. It involves incubating the disks at elevated temperature and humidity and measuring the optical read-out. This proposed test procedure is now in the first stage of balloting and it will be several years before it is published. While it represents a very significant advance in the application of optical disks for long-term storage, it must be recognized that it involves only the media. It does not address the optical disk system and the concerns about equipment deterioration and obsolescence still exist.


The tremendous advantages of optical disks are data compaction, access, retrieval and transmission. However, this technology still lacks some of the attributes required for archival storage where a long life expectancy is desired. As an interim strategy for specific archival applications, some facilities are using a hybrid system with photographic film being the storage medium and optical disks being used for access and transfer of information.

Dr. Peter Z. Adelstein is chairman of Technical Committee IT9-5, which prepares ANSI standards on permanence of imaging materials, and a research associate with the Image Permanence Institute at the Rochester Institute of Technology. His areas of work include the physical properties of plastics, gelatin, photographic film and magnetic tape. He holds a PhD in physical chemistry from McGill University.


The Commission of the European Communities has produced a practical guide and directory of permanent book paper as a way to raise awareness throughout Europe of the breadth and complexity of the problem of “millions of books turning to dust each year in our libraries.” The 31-page directory lists acid-free and permanent papers available in Austria, Denmark, Finland, France, Germany, Great Britain, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, and Switzerland. It also includes a nine-language introduction to the brittle book problem, a technical note on the self-destruction of acid-free paper, and a list of recommendations of the Experts’ Meeting Conservation of acid paper materials and the use of permanent paper, organized by the Commission of the European Communities and the Dutch government and held in the National Library of the Netherlands, December 1991. Further information on the European Directory of Acid-Free and Permanent Book Paper, which was edited by the European Foundation for Library Cooperation/Groupe de Lausanne, is available from the Commission of the European Communities Directorate-General X, Audiovisual Information, Communication, Culture, “Culture Unit”, rue de Trèves 120, B-1049 Brussels, Belgium.

Preservation Analysis and the Brittle Book Problem in College Libraries: The Identification of Research-Level Collections and Their Implications examines priorities for treatment of brittle research materials and potential contributions of college libraries to national preservation efforts. The authors conducted condition surveys in three college libraries, identified titles as curriculum support, low-use research, or special collections materials, and assessed their physical condition. The results indicate that the libraries own significant numbers of low-use research volumes that are brittle and in some cases held by few other libraries nationwide. The article was published in the May 1993 issue of the College & Research Libraries, pp.227-239.

Preservation film: platform for digital access systems

by C. Lee Jones
President, MAPS The MicrogrAphic Preservation Service, Inc.

This report is one of a series exploring new technologies for preservation and access. Previous Commission publications on film and digital technologies include: “Opto-Electronic Storage–An Alternative to Filming?” by Dr. Hartmut Weber, in Commission or Preservation and Access Newsletter, February 1993; A Hybrid Systems Approach to Preservation of Printed Materials, by Don Willis (November 1992); Electronic Technologies and Presentation, by Don Waters (June 1992); and Preservation of New Technology. A Report of the Technology Assessment Advisory Committee (October 1992).

Editorial note for electronic edition. In the printed newsletter from which this electronic version was derived, there was an error: for “line-pairs per millimeter” the printed version had “lines per millimeter“. See the April 1995 Newsletter. This error has been corrected in the text that follows.

The entire world of scholarship and research, with significant leadership from the library community, is committed to the belief that our information future will be far more digital than it is even in today’s environment, replete as it seems to be with computers and telecommunication services. A month does not pass without some development which promises to help manage our burgeoning databases more effectively, provide easier access to their contents, or provide more compact storage or high transmission speeds and greater transmission band width.

In this context, a growing group of professionals in libraries, archives, museums, historical societies, and similar organizations are equally committed to finding the most efficient ways to preserve that information created in the past which is in danger of loss through embrittlement of the medium upon which the information is recorded or through intensive use of the medium. Most of the attention has been directed toward preservation of the printed word, though graphic images, photographs, negatives, and prints are receiving increasing attention as is information preserved in magnetic and optical media. These preservation efforts are intended to preserve information for future use, a future, as noted, which will be increasingly digitally oriented. Hence, the preservation medium selected must have the capability of supporting a wide range of digital access systems.

Initial preservation reformatting efforts were focused entirely on microfilm as the medium of choice. For the last ten years or more, attention has been directed at the potential alternative media might have for preservation purposes. Rigorously precise studies indicate that the 500+ year life expectancy of microfilm, when properly prepared, stored and managed, far surpasses any other medium in terms of longevity and ability to accurately reformat information. No other technology is yet in a position to challenge film as a preservation medium for print on paper materials. While it is useful to continue the evaluation of possible alternatives, the majority of the preservation community continues to view microfilm as the only truly long term preservation alternative.

The equipment used for most preservation filming since its inception in the mid-1930’s has been the Kodak MRD line of cameras. This workhorse of the preservation filming community was not significantly altered during its 50+ years of service. Indeed, and now unfortunately, the preservation standards specific to filming, including the RLG Guidelines, have been established with the MRD cameras in mind. In fact, the standards push the operating limits of the MRD. This becomes particularly important in the area of resolution where the minimum acceptable resolution for preservation purposes is 120 line-pairs per millimeter. If we are serious about preparing our preservation film for the digital future, we must reach beyond that minimum in order to capture as much detail as possible.

Late in 199, Kodak announced that it would no longer manufacture the MRD and would not replace it with any alternative 35 mm microfilm camera. Bad news for the preservation community. However, there are alternative cameras for the high quality required to capture images for future generations.

Firms such as Gratek (England), Elke (England), Zeutschel (Germany), and Schautt (Germany) all produce cameras superior to the MRD. Probably the premier example of alternative cameras is a small firm in Garmisch-Partenkirchen, Germany, Herrmann & Kraemer, which builds its own cameras in order to achieve the quality results they expect. As Kodak abandoned the 35 mm camera field, Herrmann Kraemer began to manufacture cameras for sale. The Herrmann & Kraemer (H&K) camera is an order of magnitude superior to the MRD and to many other competing cameras as well, though there is a premium in terms of price to be paid for this quality. It is a computer controlled camera with incredibly fine adjustments for illumination, reduction, exposure time, all coupled with the finest optics available. Resolution, even when not completely adjusted, is 40% better than the MRD and with some careful tuning, can produce resolutions which are more than 60% better, in the 200 line-pairs per millimeter range.

The importance of high resolution film is based on the rule of 25.4. There are 25.4 millimeters per inch. Scanned resolution is evaluated in dots per inch. Scanning at 1,000 dots per inch sounds like wonderful resolution until one divides that(1,000 dots per inch by 25.4 to produce a comparison to film resolution. The result, for those of you without immediate access to a calculator, is just under 40 line-pairs per millimeter! Those who would suggest that we need to scan first, run up against this 25.4 rule very quickly. If they can scan at 1,000 dots per inch, and few can at this stage, the conversion to film, which can be done, will produce a film resolution of less than 40 line-pairs per millimeter. On the other hand, film of 200 line-pairs per millimeter is the equivalent in inches of over 5,000 dots per inch (200 times 25.4). Thus, the preservation community, committed as it obviously is to preserving our intellectual heritage for future use, needs to make a commitment to high resolution film which can be easily scanned into digital formats, retains more resolution than scanning technology can presently capture and precludes a dependence upon a fast changing digital environment that can leave pioneers with the unfortunate and expensive task of recapturing information in the next digitally based technological innovation. For these reasons, the preservation community must opt for the highest quality microfilm that can be produced.

A second factor which is critical to facilitating scanning of preservation film for digital access systems is the issue of density variation within a reel of film. Preservation standards allow a relatively wide range of densities on a reel of .20 density points. However, the narrower the range of densities on a reel, the more readily it can be scanned without making adjustments for swings in density. There is at least one system that is specifically designed to produce preservation film with narrow density ranges, ExpoSure(TM) developed by MAPS The MicrogrAphic Preservation Service, Inc. A US patent was awarded for ExpoSure(TM) in 1992 and it has resulted in even higher quality preservation film by coupling the high resolution inherent in the H&K with extraordinarily narrow density ranges (often less than .05 density points) on any given reel of film. These two characteristics, high resolution and narrow density ranges, resulted in film that is far more easily scanned into a variety of digital formats. Anecdotal evidence suggests that film with narrow density ranges and high resolution can be scanned with significantly fewer adjustments during the course of the scan.

Normal microfilm is a high contrast recording medium that was never designed to capture halftone or continuous tone material, photographs, negatives, prints, and heavily illustrated printed material. But, it is possible to link the capabilities of the new high resolution camera to a newly available continuous tone filming (CTF) process that successfully captures continuous tone images with great fidelity and adheres to all preservation standards. Continuous tone filming is not new, but previous techniques either used non-preservation film bases (acetate) or suffered from loss of resolution both during original image capture and during duplication. CTF technique suffers from neither of these limitations. Resolution occasionally exceeding 200 line-pairs per millimeter is achieved using this technique. While there is some loss of resolution during duplication, it is often not measurable; that is the resolution as measured from the standard test target remains the same. One measure of quality is that third generation CTF images have been taken to a reputable photo shop and high quality paper prints produced.

The preservation community now has a range of Options available in order to prepare preservation film for digital access systems. Cameras of superior quality are available, though not widely deployed as yet. Part of the reluctance to deploy new generation cameras is their cost and the lack of active demand for higher resolution. Further, as long as the acceptable density range for preservation film is as broad as it currently is, we are preparing film that will require constant adjustment during scanning operations, adjustments which will force the cost of such scanning to rise. Until the market, that is the preservation reformatting market, demands higher quality, it will be less widely available than it is now.

Digital access systems are proliferating and can be found in nearly every institutional venue in which preservation programs also exist. Some film to paper printers use scanning technology to capture the image before it is transferred to paper. Film of primarily textual material is being scanned into CD-ROM products and as the quality of film improves and more heavily used material is filmed, more and more CD-ROM products will be produced from film. CTF film has now been shown to produce superb images using Kodak’s Photo CD system, from which images can be captured by any number of software programs for distribution on floppy disks or distribution over a telecommunication network. This brand new option for preservation quality graphic images promises to open completely new access systems for graphic and text images.

Vendors of preservation filming services have focused their recent service enhancements on ways to reduce the cost of getting material onto film by offering prefilm search services, material preparation, print master storage, post film cataloging, etc. All of these services have an essential role in seeing that the most material is reformatted with available resources. However, we often lose sight of the objective, serving the information needs of the future, and concentrate on doing things as quickly and cheaply as possible now. If those current decisions result in preservation products that serve only immediate needs and fail to serve the longer term information needs of the future, our decisions will be viewed as very expensive ones by those who follow us.

The preservation reformatting goal of every library, archive, museum, and historical society needs to be to prepare preservation microfilm for the digital present and future. We can not afford to preserve materials more than once. To simply reformat endangered materials into a form resistant to scanning or one that complicates scanning is a serious disservice to scholars and researchers of the future.

Commission on Preservation and Access
1400 16th Street, NW, Suite 740
Washington, DC 20036-2217
(202) 939-3400 Fax: (202) 939-3407

The Commission on Preservation and Access was established in 1986 to foster and support collaboration among libraries and allied organizations in order to ensure the preservation of the published and documentary record in all formats and to provide enhanced access to scholarly information.

The Newsletter reports on cooperative national and international preservation activities and is written primarily for university administrators and faculty, library and archives administrators, preservation specialists and administrators, and representatives of consortia, governmental bodies, and other groups sharing in the Commission’s goals. The Newsletter is not copyrighted; its duplication and distribution are encouraged.

Patricia Battin–President
Maxine K. Sitts–Program Officer, Editor
Sonny Koerner–Managing Editor