If you are creating an image collection for a museum, library or archive you will immediately find yourself confronted with a variety of complex issues. We cover many of these in our other sections, especially Digitization Projects. As you'll discover, the practice of creating online exhibits and image collections is far from standardized, and as technology advances at such a breakneck speed the possibility for creating rigid set of guidelines in the near future seems unlikely. Nevertheless, as more Museums, Archives and Libraries work with images and web technology, a rather loose set of "best practices" seems to be emerging. Obviously, before undertaking such a project it will be necessary to carefully consider whether it will be possible to smoothly integrate such a database into the existing information management practices of your particular institution. While we can't address all these specific institutional issues here, we hope to give you some basic guidelines for considering how your database might be used both internally by the staff workers, and/or externally by the "virtual visitor."
Here are some of the key issues you need to consider as you make your scanning decisions:
When determining the goals of any digitization project, some central questions and issues to consider are:
These issues will directly affect the level of resolution or speed you require. Creating a virtual exhibit and developing an image database can be two very different ventures, with the latter being by far the most complex of the two. If you are scanning only for an online exhibit then the process can go quite quickly, with image such as photographs scanned at around 100dpi as a JPEG or GIF. These images will be fine for viewing online, but not spectacular for printing. For an image database, however, you would probably want to scan at least 600dpi (the new archival standard for Digital Preservation) and save the file as a TIFF or PNG. (This large file should not be part of a larger network, as you will want to limit access to this "original" file for the sake of preservation).
First of all you will need to consider the Key Issues surrounding digitization projects so that you can assess whether the original material is suitable for conversion. You will then need to consider how you would classify that particular document. One thing is clear, when dealing with the scanning and digital conversion of a source there is no one-size-fits all standard of operation. Different document types will require different approaches to the scanning process, and even different scanning equipment. In order to make decisions about resolution, color and format, you will need to evaluate the material in terms of medium, type, dimensions, color, level of detail, color, shadow and depth--a process you'll become more familiar with as you build your expertise.
In terms of scanning, documents are generally divided into five classifications depending on complexity and thus the type of formatting and bit-depth each image-file will require. As it is impossible to provide any specific parameters without referring to a specific document, the suggestions we give as to scanning and file resolution are intended as rough guides and refer only to the creation of Master Files that will not be viewed on the web:
1) Typed, printed materials, line-drawings, woodcuts, maps, blueprints, music scores
MASTER FILES:
Scan Resolution: 300-600dpi
File Format and Resolution: Lossless TIFF; 200-300dpi2) Manuscripts or hand-produced text that is less clear than the above materials. These include letters, line drawings, or maps
MASTER FILES:
Scan Resolution: 200-300dpi
File Format and Resolution: Lossless TIFF; 200-300dpi
3) Documents such as engravings or graphic art that is less complex than a photograph or highly detailed illustration
MASTER FILES:
Scan Resolution: 200dpi
File Format and Resolution: TIFF or GIF; 200-300dpi
4) Photographs or detailed artwork where there is a smoother variation of tones between colors. There is need for more bit-depth to display this tonal quality
MASTER FILES:
Scan Resolution: adjust the pixel dimensions to around 2,700 x 2, 700 (if a square image)
File Format and Resolution: TIFF; 600-1200 dpi
5) Mixed documents that may contain a combination of the above, such as newspapers, magazines, illustrates books, etc.
MASTER FILES:
Scan Resolution: trial and error depending upon the mix of documents File Format and Resolution: TIFF; 600-1200 dpi
DIGITAL IMAGING FOR ARCHIVISTS, LIBRARIANS & CURATORS: ONLINE RESOURCES (top)
Conservation Online CoOL, a project of the Preservation Department of Stanford University Libraries, is a full text library of conservation information, covering a wide spectrum of topics of interest to those involved with the conservation of library, archives and museum materials. Although this is more of a reference site than a "how-to" guide, Cool provides invaluable links to essays on digital imaging and preservation.
"Using Kodak Photo CD Technology for Preservation and Access: A Guide for Librarians, Archivists, and Curators" (Anne Kenney and Oya Y. Reiger) A brochure that summarizes the findings of a study--coordinated by Cornell University Library's Department of Preservation and Conservation--that evaluated Kodak Photo CD technology as a tool for preserving and making available electronically a broad range of research materials.
Image Permanence Institute (RIT) The Image Permanence Institute is a university based, nonprofit research laboratory devoted to scientific research in the preservation of visual and other forms of recorded information. (See pdf file on Digital Imaging)
Archives and Preservations by National Archives and Records Administration (NARA) This page is designed to offer guidance concerning archival preservation, management, and training to all levels of archivists and preservation professionals from the at-home record-keeper, to the family genealogist, to professionals seeking technical guidance from the National Archives and Records.
NARA Guidelines for Digitizing Archival Materials for Electronic Access Although NARA is careful to state that these guidelines should not be seen as a set of standards for digital imaging, this report offers excellent advice for digitization projects.
Preservation of Library and Archival Materials: A Manual (Full Online version available)
Selecting Research Collections for Digitization by Dan Hazen, Jeffrey Horrell, Jan Merrill-Oldham This invaluable book is available as a full online version. See especially, "Selection for Digitizing: A Decision-Making Matrix" , a very useful graphic aid for considering the various steps to selecting and processing images for a database.
Research Library Group: Diginews (December 1997) RLG is a not-for-profit membership corporation of institutions devoted to improving access to information that supports research and learning. The home site describes their activities and services, offers assistance to their members and users, and shares news. Although this particular issue is a couple of years old, Frey's "Digital Imaging for Photographic Collections" is useful.
"Digital Libraries: A Selected Resource Guide" by K. Klemperer & S. Chapman. An extremely comprehensive resource guide to the major publications and educational sites in the field. The essay covers many issues, including quality standards, technology products, and source selection.