Berkeley Digital Library SunSITE

Example Decisions on Digital Image Formats

The following is an excerpt from a report of the UC Berkeley Library ad hoc Format Task Force, submitted June 12, 1995. The recommendations are related to pictorial imaging preservation and network access needs of a particular library. They are offered here as an example of the kinds of decisions that libraries must make regarding these issues. TF members included Campbell Crabtree, Eva Garcelon, John Hassan, Glen Jackson, Dan Johnston, and Barclay Ogden.

  1. Make a distinction between archival files and viewing files, the former to be used as a source for the latter, the latter to be determined by limitations of transmission and display.
  2. Capture for the archival file as much information as possible, using color rather than grayscale where there is any any color information in the original documents. Archival files should be lossless, as close to 600 dpi as possible, 24 bit RGB or 8 bit grayscale TIFF (due to the universality of the format), and should be stored off line until the Library acquires a mass storage capability. For the current projects, the Kodak Photo CD files can serve as archival files with the expectation that they will be converted and migrated in due course.
  3. Viewing file should be JPEG (w/24 bit color). The format can be opened by PC and X versions of Netscape and Mosaic (recent release), Dynatext, and several stand-alone viewers including xv, LView, SYSView, and JPEGView.
  4. The viewing file should have a target file size limit of 200K, compressed. Anything larger than that leads to too slow performance with current systems for general use. Smaller files are even more desirable where VGA-optimized image quality remains acceptable.
  5. Guidelines for use of JPEG compression options should be developed after the Library has gained experience with a range of image types, taking into consideration image quality (incl. artifacts of compression) and file size.
  6. All production projects should check periodically the openability of the project files by the viewers of choice to ensure ongoing compatibility.

Copyright © 1995 UC Regents. All rights reserved.
Document maintained at http://sunsite.berkeley.edu/Imaging/formats.html by the SunSITE Manager.
Last update 11/1/95. SunSITE Manager: manager@sunsite.berkeley.edu