A Hybrid Systems Approach to Preservation of Printed Materials


Handling Pages--Little Difference in the Cost: Michael Lesk, in an earlier report published in 1990 by the Commission on Preservation and Access entitled "Image Formats for Preservation and Access" (July 1990), concludes that microfilming a book costs about 10 to 15 cents per page. Digital image scanning was pegged at between 13 and 28 cents per page.[16] Our research indicates that current filming costs are slightly higher, and preservation imaging costs are about double those quoted by Lesk. The higher costs for preservation filming can probably be attributed to inflation and experience with the difficulties and corresponding costs of preservation filming. The higher costs for digital imaging can be attributed to the higher resolution scanning, and the high cost of storing these archival resolution images on optical disc.

However, the new generation of vacuum-fed, belt-driven, duplex scanners which have recently become available for handling non-brittle materials, along with the reduction in optical disc media costs, promises to reduce page imaging costs substantially. Some of these new scanners can capture both sides of a page in one second which is faster than any planetary camera; in addition, the newest ones can film the page simultaneously, using a planetary camera that is mounted on a camera stand above the feed belt. Of course, platen scanners and through-the-lens scanners are also available for handling brittle materials in a very safe and efficient manner. These new developments guarantee that scanning costs should be no greater for digital imaging than for filming.

While page handling is one of the most costly function of preservation, one should not lose sight of the fact that the materials selection and acquisition process is also very expensive, so we want to make sure that whichever storage strategy is selected, the process does not have to be redone.

Cost of a Digital Image Preservation System

Regardless of which technology is chosen, the cost and technology necessary to implement and operate a preservation system is significant. For all but the larger institutions, these barriers could be insurmountable.

Note: The digital system implementation costs that follow have been increased by 50% from those presented in the reference (see endnote 17) to compensate for the fact that a preservation system must be implemented using archival resolution with technology available at time of publication.

It's interesting to note that when viewed on a per-page basis, the cost to implement the digital image systems described below range between $0.15 - $0.50, regardless of the size of the page. For further explanation of how resolution affects cost see Appendix A.

Digital system implementation costs: Digital image systems are usually configured to a certain capacity level:* Stand-alone microcomputer-based systems: This system is capable of non-critical workloads up to 300,000 pages per year. Some 47 percent are priced at less than $60,000, another 40 percent between $60,000 and $150,000. ($0.24 - $0.50 per page)

Networked microcomputer-based systems: Depending on design, these systems are capable of critical workloads of between 150,000 and one million pages per year. Some 23 percent cost between $60,000 and $150,000, 70 percent over $150,000. ($0.20 - $0.40 per page)

Minicomputer [or microprocessor]-based systems: Capable of workloads from one million to five million pages per year. Sixty-nine percent cost under $450,000, 27 percent range from $450,000 to $750,000. ($0.15 - $0.45 per page)

Mainframe [or multi-processor]-based systems: Designed to handle workloads of over three million pages per year. Forty percent cost under $450,000, 33 percent between $450,000 and $750,000, and 27 percent over $750,000.[17] ($0.15 - 0.25 per page)

The components of a typical digital image system are listed in Figure 8.

Digital system operating costs: The cost of creating a digital page image, indexing it, and storing it on optical disc on a custom-designed in-house system is between $0.30 and $1.20 per page, depending on volume, size, type of documents, condition, amount of halftone content, amount and type of indexing, resolution, and amount of image processing required. Capturing a binary 300-dpi image of a good-quality text page, compressing it, and storing it on optical disc with simple indexing can be done for between $0.30 and 0.55 per page. On the other hand, capturing an archival resolution image with greyscale, complicated indexing, and image enhancement will cost between $0.50 and $1.20 per page. (Estimated prices originate from actual experience modified by an informal survey of image processing sites by the author.)

Contract preservation imaging costs: Contract preservation imaging is estimated to cost between $0.50 and $2.50* per page. Capturing a binary 300-dpi image of a good-quality text page, compressing it, and storing it on optical disc with simple indexing can be done for between $0.50 and 1.25 per page. On the other hand, capturing an archival resolution image with greyscale, complicated indexing, and image enhancement will cost between $1.00 and $2.50 per page. The above costs include indexing and storage on optical disc. (Estimated prices originate from actual experience modified by an informal survey of image processing sites by the author.) These costs may seem quite a bit more costly than in-house scanning; however, if all direct and indirect costs are included, and intangibles are factored in, contract scanning would probably be found comparable. It should be noted that image service bureaus can provide expertise, guaranteed workmanship, liability, and diverse equipment relieving the burden on the institution to provide these facilities or hire and train staff. However, the selection of the imaging service bureau must be done very carefully since most are unfamiliar with the quality requirements necessitated by preservation processing and tend to underestimate the costs involved. Preservation imaging should also be more costly than preservation filming.

Optical disc drives and media costs: The typical 12-inch optical disc player costs $16,000 and uses double-sided discs that have total capacity of about 4 GB each and cost about $300 when purchased in quantities.[18] The cost to store an archival resolution book size page on a 12-inch disc is about $0.085 per page (media only).

The typical 5 1/4-inch optical-disc player costs $3,000 and uses a double-sided disc with a total capacity of about 600 MB and an average cost (purchased in quantities) of $100.[19] The cost to store an archival resolution book size page on 5 1/4-inch disc is about $0.19 per page (media only).

These costs double to $0.17 and $0.38 respectively for journal size pages.

Cost of a Micrographics System

Expected workload: As with digital systems, micrographics-based preservation systems can be configured based on expected workload. An experienced operator can film about 200 exposures per hour (2 pages per exposure). This works out to about 9 seconds per page, 3,000 pages per 7.5 hr shift, or about 750,000 pages per year, per operator. The Cornell/Xerox project has achieved scanning rates (600 dpi binary) of over 1,500 images per day for three weeks.* This is about half the rate achievable for film operators; however, it includes some indexing and QC. At a fully loaded labor cost of $12.00/hour, the filming costs work out to about 3 cents per page, with another 1.5 cents for QC. Add in system depreciation, film costs, duplication costs, packaging and labeling, retakes, storage, handling, insurance, facilities overhead and profit, and we arrive at a cost of about 15 cents/page for filming the best materials. Filming old or brittle materials could easily double the cost.

Micrographics system implementation costs: Naturally, different sizes of micrographic preservation systems are required for different preservation projects. It's interesting to note that when viewed on a per-page basis the cost to implement the micrographics system described below range between $0.04 - $0.35. These are about 1/3 less than the costs to implement a digital image preservation system of comparable capacity, and are based on purchasing refurbished cameras.

A one-camera system, low-speed processor system: This system is capable of non-critical workloads of up to 500,000 pages per year. Costs are between $70,000 and $90,000. ($ 0.14 - $0.18 per page) See Figure 9a.

A multiple-camera, low-speed processor system: Depending on design, capable of critical workloads of between 650,000 and three million pages per year. Costs are between $150,000 and $250,000. ($0.08 - $0.38 per page) See Figure 9b.

A multiple-camera, medium-speed processor system: Capable of workloads from two million to five million pages per year. Costs are between $250,000 and $400,000. ($0.05 - $0.20 per page) See Figure 9c.

A multiple-camera, high-speed processor system: Designed to handle workloads over four million pages per year. Costs are between $400,000 and $800,000. ($0.10 - $0.20 per page) See Figure 9d.

NOTE: Large-scale film processing operations require air conditioning and humidity control, chemical holding, storage, disposal facilities, and silver recovery facilities.

Micrographics system operating costs: The cost to perform in-house preservation filming is estimated at approximately $0.10 to $0.18 per page*. However, it is doubtful that these costs include any indirect or overhead components. Also, in order to operate an in-house facility the institution must deal with the following issues: l) air conditioning and humidity control, 2) building a darkroom to house the processor and for handling film, 3) plumbing for the processor, 4) designating a secure storage space with a controlled environment for storing the camera negatives, S) accumulating the necessary test equipment (both chemical and photographic) needed to create high-quality film, and 6) hiring a photographic technician or engineer to run the operation.

Contract microfilming costs: As with contract scanning, contract preservation microfilming may appear at first glance to be more expensive than in-house filming; however, in actual fact, if all the in-house costs were accounted for, preservation microfilming would be found comparable. In addition, a service bureau can provide expertise and advice, material preparation, liability, processing, bibliographic services, and diversity of equipment, among others. The cost of creating microfilm at a service bureau is between $0.07 and $0.50 per page. Micrographics service bureaus charge between $0.07 to $0.15, averaging $0.08 per page to create 16mm standard document storage film. On the other hand, preservation microfilming vendors charge between $0.10 to $0.50 or more, averaging about $0.15 per page to create archival microfilm.* The distinction here is important. Preservation microfilming is more costly because of the higher standards and more stringent processing requirements. Preservation microfilming costs include creation of the master and two copies, quality controlled, labeled, and packaged. Polysulfide treatment can be added for about $3.50 per reel ($9.00 for all three copies). This does not include any automated indexing. Without indexing, of course, access is restricted.

Film storage and duplication costs: 35mm camera negative silver gelatin film costs about $0.10 - $0.12 per foot; silver print film costs about half that amount. Given that on the average one can store 12 frames per foot with two exposures per frame; and if the original camera negative is stored in a vault as the archival copy and two other copies are made--one for reprinting and one for the end-user--the film cost to preserve a page (making all three copies as described above) is about $0.01 (cost of film only). Additional copies can be made on silver duplicating film quickly and at relatively low cost using a roll-to-roll contact microfilm printer ($15 per reel at time of filming, double that later). Silver film is a requirement for preservation filming.

Preservation Cost Summary: Currently, film is the most economical technology for preservation (see Appendix D). However, the micrographic based preservation system is expected to become more expensive to operate over time simply because it is labor intensive and the cost of labor will continue to increase, while advances in micrographic technology will not increase productivity enough to offset these increasing labor costs. On the other hand, for the digital preservation systems, productivity increases will result from rapid technology advances, which are expected to accelerate rapidly over the next several years.

The practitioner should therefore become familiar with digital technology and begin planning for its use. Currently, the best use of imaging technology for preservation is to provide selective access capabilities at adequate binary resolution to the preserved collection. High-resolution, archival-quality, greyscale scanning is still expensive. It will be about another year or two before a combination of decreasing prices and advances in computer and imaging technology will make an archival resolution image preservation system cost-effective.

Finally, the institution could decide to follow the approach pioneered by Cornell, which is to create a high-quality copy on acid-free paper from scanned data at 600 dpi binary. The idea is to create a permanent, not archival, copy that can go back on the shelf. A copy could also be kept for archival processing sometime in the future. The Cornell results show quality of the output document equivalent to or in some cases, better than the original. The solution is inexpensive, practical, and effective.

Conclusion: The requirement for high-resolution greyscale imaging and the cost of optical disc storage is a major reason why archival preservation using imaging technology is still substantially more costly than archival filming. Film is the least costly storage media. A 125-foot roll of film, created to RLG preservation specifications, can contain about 2,700 nine inch pages at a reduction ratio of 12X with two pages per frame. The film cost is approximately $15.00. The same number of archival resolution images (9 X 5 inch page 600 dpi with 8 bits/pixel compressed 15:1) would require 3.0 GB of storage space. That's the equivalent of about one Write-Once Optical Disc at a cost of about $300.00. In this particular example, optical disc storage costs are 20 times more expensive than film. However, advances in imaging technology, cost reductions in the digital storage costs, and increasing costs for preservation filming argue for using film as necessary to satisfy critical needs, but beginning the switch to the hybrid digital image preservation system as soon as technically feasible. In fact, if the objectives of the system do not require high-resolution greyscale scanning (i.e., very few halftone pictures, as is the case for the materials being preserved in the Cornell Project), and the 600-dpi resolution offered by, for example, the Xerox DocuTech system, is considered adequate, then the practitioner will probably find digital imaging equivalent to filming in cost.

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Timestamp: Sunday, 23-Nov-2008 15:20:24 PST
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