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Digitization Standards for Cole County Historical Society




Cole County Historical Society, like most other agencies which are archiving digital images of historic significance, generally subscribe to the digitization standards set forth by the National Archives and Records Administration (NARA). Not necessarily in strict adherence to those standards; but loosely fitted to the mission of the archiving agency. Those standards as set forth may be found as a PDF document acessed from the digitization page, http://www.archives.gov/preservation/technical/guidelines.html , with the actual standards document found at: http://www.archives.gov/preservation/technical/guidelines.pdf.

A loose restatement of these standards for the purposes of archiving digital images at Cole County Historical Society are as follows:

  1. Archival Images will be in uncompressed TIFF format.
  2. Images considered to be black & white will be scanned in 8 bit grayscale.
  3. Images considered to be color will be scanned in 16 bit or 32 bit RGB (no 48 bit).
  4. Images will be scanned in the following resolutions 100, 150, 300, 450, 600, 750, 900, 1200 or 1600 dpi.
  5. The appropriate resolution above will be selected to produce an absolute resolution of 4000 pixels or greater on the longest dimension of the image.

The Tiff image format, without LZW compression, is specified as the archival image format because it is a bitmapped image format which is a lossless format. It can be edited and re-edited without subsequent losses after each save. It does, of course, produce quite large image files; but provides the highest quality possible for images in the archives.

Images that are considered to be "black & white", when scanned as grayscale, will produce an image file requiring approximately one-third the file size of an image scanned as RGB color. Please scan "black & white" images as grayscale.

Images that are truly color or images that were originally black & white that have aged to produce that beautiful sepia color should be scanned as 16 bit or 32 bit RGB color images.

The most difficult task is selecting the proper scanning resolution. As an example, we will select a 5" X 7" photo as the image for scanning. Seven inches is the longest dimension and we will want to scan at a resolution (100, 150, 300, 450, 600, 750, 900, 1200 or 1600) which will produce an absolute resolution for that longest dimension of 4000 pixels or greater. If we would scan that image with the 7" dimension at 600 dpi (7 inch X 600 dots per inch = 4200 dots [pixels]), it would produce an absolute resolution of 4200 pixels for that 7" dimension. Generally, this would be the appropriate scanning resolution. Here is where judgement enters into the scanning considerations. If the content of the image or the quality of the image is exceptional, step up to the next greatest scanning resolution (750 dpi) for the scan. Conversely, if the quality of the image or its' content is less than good, step down to the next lower scanning resolution (450 dpi) for the scan. A table of scanning resolutions follows:





©2014-2016 - Cole County Historical Society    109 Madison St.    Jefferson City, MO 65101         (573)-635-1850         cchs@socket.net
The Cole County Historical Society continues to be the repository to archive the history of Cole County, Missouri and is essentially operated with volunteers.