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Mocavo

Some people eat, sleep and chew gum, I do genealogy and write...

Wednesday, December 21, 2011

Digitizing like the pros

If you do any investigation at all of the parameters for scanning documents for archival preservation, you will quickly find a rather broad spectrum of recommendations. But what do the professional archivists do if they have all of the possible options? Fortunately, we have a pretty high degree of transparency from the Library of Congress. They probably spend as much time agonizing over file formats, dpi and such as anyone I can find on the Web. One example is the current digitization project being conducted by the Copyright Office of all the copyright records.

The first project, consisting of 2.5 million catalog cards constituting the indexes to assignments and transfers of copyrights from 1870 to 1977 has already been completed. The second project, digitization of the 7.7 million registration catalog cards from the period 1971 to 1977, has also been completed and over 2.4 million cards from the 1955 to 1970 have been scanned. They are continuing the scanning.

The third project is the 660 bound volumes of the Catalogs of Copyright Entries of which 417 volumes had been scanned as of December, 2011.

Now, what scanning parameters were they using to scan all of these millions of documents? Here is there explanation,
For optimal preservation, the records will be scanned in uncompressed tagged image file format (TIFF) at a minimum of 300 pixels per inch (ppi) in 24 bit color. For routine access to the digitized records, derivative files will be created in high quality JPEG and JPEG2000 format at 50:1 compression.
For the record, I now scan my own documents at 400 dpi, 24 bit color and also save the files as TIFF images.  What do other archivists do? It isn't surprising, but most follow the standards being espoused by the Library of Congress. See for example, Proposed Digital Imaging Standards and Best PracticesIndiana Memory and LSTA Digitization Projects

But what about photographic images rather than documents? Are the scanning parameters different? Here is a link to the Federal Agencies Digitization Initiative Still Image Working Group's Technical Guidelines for Digitizing Cultural Heritage Materials: Creation of Raster Image Master Files. You will find that the recommendations are very similar to those for documents, but they are very specific as to the size of the output.  

So now you know.

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