Hybrid Systems–Introduction

Comparing Micrographics and Digital Technology: This paper will focus on questions about the use of micrographics and digital imaging technologies for preservation of printed materials. It will not address any of the issues involved in the preservation of sound, motion pictures, video, art, or color images. The author is aware that other document preservation issues exist; however, it was felt that these two technologies were of most interest to the preservation community at this time. Topics to be covered include:

  • What are the advantages and disadvantages of each technology?
  • What are the trade-offs involved in selecting one technology over the other?
  • What are the benefits of a hybrid approach?
  • In a hybrid system, should the page be captured first to film and converted to digital, or vice versa; or can it be done simultaneously?
  • What options are available for converting from film to digital and back?
  • What are the cost factors; how does one maximize image quality while minimizing cost?
  • What role should ASCII* text and OCR (optical character recognition) play?
  • How can the required resolution be determined, and what are the resolution issues with each technology?
  • What standards should concern the practitioner?

Areas of Analysis: There are three primary areas of analysis in comparing digital electronic image systems to film-based systems for preservation: document capture, storage, and access. In capture, the analyst will be concerned with the capture mechanism, resolution, quality of the captured image, acquisition speed, system cost, operating cost, and indexing requirements. In storage, the concerns are media permanence, media refresh requirements, technology obsolescence, drive cost, media cost, interchangeability of media, reliability, performance and access tradeoffs. Finally, with regard to access, the designer must examine retrieval capability (both searching and browsing), retrieval speed, transmission and distribution capability, and retrieval quality. Micrographics and imaging technologies can complement each other and best address these concerns together in the well-designed preservation system.

This paper will survey micrographic and digital technologies in light of the issues and concerns defined above. The objective is to arrive at short and long-term recommendations for developing document preservation systems based on these technologies.

Executive Summary: Based on a review of the technology, our findings are:

  • Design objectives are extremely important: The preservation systems designer must identify the objectives of the preservation system in detail. For example, if practitioners desire to preserve a faithful reproduction of the document, do they want the page as it currently exists complete with its discoloration due to age and water stains, or do they desire a cleaned up page, similar to what was originally published? Obviously, an image can only be cleaned up by using electronic technology, so system requirements have a definite impact on the technology that must be used.Other important system design criteria include the volume of the workload, quality required, methods for storing and accessing the documents, frequency of access, urgency of access, response-time requirements, condition of the documents, and page sizes*.
  • A micrographics-based preservation system is a generally acceptable solution here and now for most printed materials. It is a mature technology with widespread familiarity and a large installed base. High-quality film created and stored according to standards will last up to 500 years.
  • Centralized master vaults already exist where over 3 million rolls of film masters are stored in secure, climate-controlled conditions for only about $1.00 per reel per year.
  • Microfilm’s major weakness is its inadequate access and distribution characteristics.
  • Although microforms are currently a relatively inexpensive preservation medium for printed materials, costs for this type of solution will increase at five to ten percent per year due to the increasing cost of labor.
  • Micrographics cannot be considered an acceptable solution for all preservation needs; for example, it is not ideal for preserving high-quality greyscale images, color images (e.g., artworks), sound recordings or full motion video. In these areas, digital technologies are the only reasonable alternative.
  • It can be twenty times more expensive to store 9 X 5 inch archival resolution page images on optical disc than on 35mm film.
  • For digital preservation systems, productivity increases will be brought on by technology advances, and these advances are expected to accelerate rapidly over the next several years.
  • There are no forms of digital storage currently on the market that would be considered archival according to the traditional definition.
  • Write-once optical disc could be considered permanent* but not archival. The reason is not the longevity of the media–it’s the fact that the technology becomes obsolete. Even if the media were to last 50 years, chances are there wouldn’t be a drive available to play it.
  • Perhaps when referring to digital storage media, “archival” needs to be redefined as the ability to recreate an exact copy from the original medium before it degrades or the technology necessary to read it becomes obsolete.
  • Assuming that refreshing of media (recopying) would be cost justified by the increase in capacity and/or reduction of cost of the new media, a key question preservationists must answer is, “Is a solution acceptable which requires the media to be recopied onto more advanced media every “N” years in order to keep up with advancing technologies?” If so, who would be in charge of assuring that the conversion was carried out on schedule? This whole topic could be the subject of a new paper.
  • A digital image based preservation system is the most promising future solution for printed materials. It is a rapidly changing technology in quality, speed, and economics. Its major weaknesses are that the technology is fairly new, has high data-storage requirements, and lacks proven archival storage capability.
  • Digital imaging technology will increase in functionality and decrease in cost for the foreseeable future. Many experts believe that an all-digital system will provide the most economical future preservation solution. In fact, if one were to do a five year present value analysis of a micrographics based versus a digital image based preservation system today, factoring in the costs of access and distribution, the digital system would most likely prove to be the least expensive alternative.
  • Access to the preserved materials is a key benefit of the digital image preservation system. Access can be through a separate database of indexes, abstracts and indexes, full-text search on the ASCII portion of compound documents, or by browsing through the database item by item.
  • With digital technology it will no longer be necessary for the researcher to travel to where the preserved materials are physically located; access to historic collections throughout the country can be as close as the nearest computer or printer.
  • For digital preservation systems, productivity increase will be brought on by technology advances, and these advances are expected to accelerate rapidly over the next several years.
  • There are no forms of digital storage currently on the market that would be considered archival according to the traditional definition.
  • Write-once optical disc could be considered permanent3 but not archival. The reason is not the longevity of the media–it’s the fact that the technology becomes obsolete. Even if the media were to last 50 years, chances are there wouldn’t be a drive available to play it.
  • Perhaps when referring to digital storage media, “archival” needs to be redefined as the ability to recreate an exact copy from the original medium before it degrades or the technology necessary to read it becomes obsolete.
  • Assuming that refreshing of media (recopying) would be cost justified by the increase in capacity and/or reduction of cost of the new media, a key question preservationists must answer is, “Is a solution acceptable which requires the media to be recopied onto more advanced media every “N” years in order to keep up with advancing technologies?” If so, who would be in charge of assuring that the conversion was carried out on schedule? This whole topic could be the subject of a new paper.
  • A digital image based preservation system is the most promising future solution for printed materials. It is a rapidly changing technology in quality, speed, and economics. Its major weaknesses are that the technology is fairly new, has high data-storage requirements, and lacks proven archival storage capability.
  • Digital imaging technology will increase in functionality and decrease in cost for the foreseeable future. Many experts believe that an all-digital system will provide the most economical future preservation solution. In fact, if one were to do a five year present value analysis of a micrographics based versus a digital image based preservation system today, factoring in the costs of access and distribution, the digital system would most likely prove to be the least expensive alternative.
  • Access to the preserved materials is a key benefit of the digital image preservation system. Access can be through a separate database of indexes, abstracts and indexes, full-text search on the ASCII portion of compound documents, or by browsing through the database item by item.
  • With digital technology it will no longer be necessary for the researcher to travel to where the preserved materials are physically located; access to historic collections throughout the country can be as close as the nearest computer or printer.
  • Efficient access to the preserved collections has the potential of allowing the institution to self-fund some of the preservation costs through revenues generated from the improved access to the archival collection.
  • An inexpensive solution to preservation has been explored in a pioneering project of Cornell University. They have used digital scanning at 600 dots per inch (dpi) binary, to create high-quality copies on acid-free paper. The idea is to create a permanent, not archival, paper copy that can go back on the shelf– preservation reformatting.
  • A hybrid system, one that combines both film and digital imaging, could well offer the best overall design for current preservation needs. Micrographics provide a relatively inexpensive, high-quality archival storage medium. Digital imaging contributes access, distribution, and transmission strengths. It should be noted that in the near future, most national service bureaus will have the capability to transfer from one technology to the other, so the practitioner need not design the full hybrid capability into the local system.
  • A hybrid system can be implemented with today’s technology by filming first and scanning some or all of the film to enhance access to the preserved collection. We will designate this as the “film-first archival preservation system.”
  • The latest possibility for implementing a hybrid system is through filming and scanning simultaneously. New belt-fed combination duplex scanner/filmer image capture devices were introduced at the 1992 AIIM show by Bell & Howell and Kodak. These devices could be used on non-brittle documents. As far as processing goes, this type of system suffers from some of the same limitations as the film-first system which will be discussed later.
  • The “scan-first archival preservation system” is rapidly becoming an acceptable alternative for the preservation system designer. By scanning first, each page can be decomposed into separate areas of text, line art, and halftones. Each of these will be electronically processed independently to maximize overall page quality. By scanning in greyscale and enhancing the digital data prior to creating film, it will be possible to create higher quality film than can currently be created using light/lens methodology.
  • Scanning first will also allow more intelligent retrieval aids in bar code format or blip marks to be recorded onto the film so that retrieval can be automated.
  • Digital imaging allows end-users to obtain higher quality printed copies than micrographics. Each copy will be a first-generation copy. As with music on a compact disc, there is no degradation during usage. Because of the aforementioned, the scan-first archival preservation system will be more cost-effective to build and operate than any other type of preservation system once all the technology is available.
  • Resolution is the key design parameter for a digital image preservation system (see Appendix A). We’ve defined various levels of resolution referred to in this paper as follows:
    • “Archival resolution” is defined as the resolution necessary to capture a faithful replica of the original document, regardless of cost.
    • “Optimal archival resolution” is the lowest resolution that will completely satisfy the archival image objectives defined for the system.
    • “Adequate access resolution,” on the order of 300 dpi binary, is defined as the resolution sufficient to capture about 99.9 percent of the information content of the page.
  • Microfilm is “resolution-indifferent”. Each frame of film can store high-quality images with equivalent digital resolution of about 800 to 1,000 dpi with about 8 – 12 levels of greyscale.
  • Digital imaging is “resolution dependent”: the higher the resolution requirements, the higher the cost and complexity of the system.
  • The above suggests a second question pertaining to resolution that must be answered if we are to accurately evaluate our alternatives. It is “should film standards, which primarily measure the high contrast components of a reproduction, be used to measure digital reproducibility?” Do we want to have perfect print or a high-quality copy of the entire original including halftones.

Recommendation: Currently, practitioners choosing microfilm for a preservation solution can feel confident that their printed materials will be adequately preserved and that even in the next century or beyond the technology will be available to transfer this material to other media if desired. This is true because of its accepted archival nature, and the fact that one only needs a lens and light to read it. Optical storage can be considered for preservation on a selective basis provided there is a plan to recopy the media prior to any substantial degradation. For the longer term, practitioners should immediately begin planning for, and designing, the hybrid archival preservation system of the future. The continuous and accelerating improvements in electronic imaging and optical disc technology will be the key to solving preservation problems.