CXP placed primary emphasis on the production in a timely and
cost-effective manner of printed facsimiles that consisted largely of
black-and-white text. With binary scanning, large files may be
compressed efficiently and in a lossless manner (i.e., no data is lost in
the process of compressing [and decompressing] an image--the exact
bit-representation is maintained) using Group 4 CCITT (i.e., the French
acronym for International Consultative Committee for Telegraph and
Telephone) compression. CXP was getting compression ratios of about
forty to one. Gray-scale compression, which primarily uses JPEG, is much
less economical and can represent a lossy compression (i.e., not
lossless), so that as one compresses and decompresses, the illustration
is subtly changed. While binary files produce a high-quality printed
version, it appears 1) that other combinations of spatial resolution with
gray and/or color hold great promise as well, and 2) that gray scale can
represent a tremendous advantage for on-screen viewing. The quality
associated with binary and gray scale also depends on the equipment used.
For instance, binary scanning produces a much better copy on a binary
printer.
Among CXP's findings concerning the production of microfilm from digital
files, KENNEY reported that the digital files for the same Reed lecture
were used to produce sample film using an electron beam recorder. The
resulting film was faithful to the image capture of the digital files,
and while CXP felt that the text and image pages represented in the Reed
lecture were superior to that of the light-lens film, the resolution
readings for the 600 dpi were not as high as standard microfilming.
KENNEY argued that the standards defined for light-lens technology are
not totally transferable to a digital environment. Moreover, they are
based on definition of quality for a preservation copy. Although making
this case will prove to be a long, uphill struggle, CXP plans to continue
to investigate the issue over the course of the next year.
KENNEY concluded this portion of her talk with a discussion of the
advantages of creating film: it can serve as a primary backup and as a
preservation master to the digital file; it could then become the print
or production master and service copies could be paper, film, optical
disks, magnetic media, or on-screen display.
Finally, KENNEY presented details re production:
* Development and testing of a moderately-high resolution production
scanning workstation represented a third goal of CXP; to date, 1,000
volumes have been scanned, or about 300,000 images.
* The resulting digital files are stored and used to produce
hard-copy replacements for the originals and additional prints on
demand; although the initial costs are high, scanning technology
offers an affordable means for reformatting brittle material.
Public-domain text, read in full here on John Shaqi.
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