By Kate Murray
The following is a guest post from Carla Miller of the Library of Congress. This is the second in a two-part update on the recent activities of the Federal Agencies Digitization Guidelines Initiative. This article describes the work of the Still Image Working Group. This article describes the work of the Audio-Visual Working Group.
While attending a Federal Agencies Digitization Guidelines Initiative Still Image Working Group meeting earlier this summer, I suddenly saw everything come together. What I mean by that is I realized how the digital preservation work performed by my team at the Library of Congress intersects and relates to the work being performed by other divisions within the Library as well as other government agencies.
At the Library of Congress, Dr. Lei He is an imaging scientist who is currently researching the effects of compression on digital images. Dr. He also uses quantitative methods to analyze edges found in images. “Edges” are naturally occurring high contrast areas of photographs that can be used to determine what resolution is needed for digitization. Dr. He’s research is already improving the processes at the Library of Congress. Similar analyses done on the Farm Security Administration photo collection at the Library determined a higher scanning resolution was required for groups of negatives in the collection. This determination was especially significant because many historic negatives are deteriorating, which means this may be the last chance to digitize them for preservation and access.
Another type of research and testing is being done by Don Williams of Image Science Associates, an expert consultant for the Library of Congress. Don works with Steve Puglia and Dr. Lei He at the Library to develop software and image targets for assessing image performance. The software is known as DICE (Digital Image Conformance Evaluation), and using targets it analyzes the quality of the actual image capture to help determine both if the product quality expected is occurring and if that quality is consistent throughout the workflow. One important aspect of the DICE targets is that they are produced with spectrally neutral gray patches; many neutral patches on color/grayscale targets are not. A spectrally neutral target for transmissive materials (think photographic negatives rather than printed photos) is also in development.
The Library of Congress uses the DICE targets to test scanning equipment and to verify output quality. The DICE software is also used in quality assurance and quality control testing for digitization projects funded by the Library. This testing and analysis assures consistent quality across projects. It also ensures that the final product will be as true to the original as possible, an aspect that is often important for users of the Library’s digitized collections.
In a joint effort with the Government Printing Office and the National Archives and Records Administration, Library staff members have developed a matrix of file format comparisons. Five formats for still images were chosen for analysis: PNG, TIFF, JPEG, JPEG2000 and PDF. The group compared sustainability, and cost factors for implementation and storage. The final draft of this document will be available for public comment on the FADGI site within the next couple of weeks.
The research work being done at the Library benefits other Federal agencies as well. In fact, the entire purpose of FADGI is for Federal agencies to collaborate and share information and best practices on digitizing our various collections and records. Some examples of these collaborations were shared at our most recent meeting: Don Williams will be working with the National Anthropological Archives at the Smithsonian on the digitization of endangered manuscript materials. The Smithsonian will work with the Library on standardized language we use in contracts requiring the use of DICE targets as an objective measurement of scanning devices. And in a general sense, the research we do often informs the development of policies, protocols and workflows throughout the Library and various other agencies.
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