-------- Original Message --------
Subject: FW: scanning encapsulated maps
Date: Thu, 29 Apr 2004 16:15:26 -0400
From: Erich Kesse <[log in to unmask]>
------------------
Your message was forwarded to the University of Florida's Digital Library
Center by the UF Map Librarian.
I advise scanning in advance of encapsulation, the primary strategy of the
University of Florida, or -- barring that -- encapsulating with extra margin
for future removal and re-encapsulation.
Scanning through polyester is certainly possible but raises a number of
issues including:
** Moire ... and similar visual effects
Polyester films will impart these visual effects. These will be more
apparent with modern maps printed with half-tone technologies (... or
painted by Roy Lichtenstein).
** Gamma ... and other tonal/color curve variation
If faithful color reproduction is a goal, you will find that some types of
polyester films introduce a grey quality -- almost all shift color-curves ::
but this is probably the least of your worries re: color fidelity.
Color-curves may be corrected with minor difficulty by skilled individual
with access to an unencapsulated copy (or with an analyzed sample-scan of
the polyester used for encapsulation -- not all polyester films are the
same).
** Glare
Lights can be positioned to mitigate glare effects. But, if the
encapsulated map-of-size has been used, it will likely have dents and dings
that make glare mitigation difficult to impossible.
UF, generally, removes maps encapsulated under previous policy (pre-digital)
from polyester. IF you must encapsulate in advance of digitization,
consider adding vacant margin on two sides ... making the encapsulation
bigger than needed for future opening and re-encapsulation.
** Plate block distortion
Again, if faithful reproduction requires ability to "read" plate block
impressions, imaging through polyester will distort the visual impression of
the plate block.
** Flatness ... or the lack thereof during imaging
Large map encapsulation processes are notoriously bad at vacating air from
the encapsulation. Large maps should be imaged on a vacuum table to ensure
flat image capture, without distortion. Effective use of vacuum table will
require removal from polyester.
Polyester will also introduce distortions should you decide to use a
plotter/digitizer. [Heaven forbid it -- use of a plotter/digitizer is like
scratching of finger nails on a chalkboard, with or without polyester!]
If you intend to geo-rectify these map images for use in GIS, even minor
distortion and glare may have a significant impact on the process.
Best of luck.
Erich Kesse
Digital Library Center, University of Florida
The PALMM World Map Collections: http://palmm.fcla.edu/map/
-----Original Message-----
From: Johnnie D. Sutherland [mailto:[log in to unmask]]
Sent: Wednesday, April 28, 2004 11:58 AM
To: [log in to unmask]
Subject: scanning encapsulated maps]
-------- Original Message --------
Subject: scanning encapsulated maps
Date: Wed, 28 Apr 2004 09:49:22 -0500 (EST)
From: Travis Dolence <[log in to unmask]>
------------------
I am starting a major campaign of map encapsulation. However, at some
point I would like to scan a number of these maps. Is it possible to scan
encapsulated maps, will it hurt the scan quality? Any help that people can
provide would be appreciated.
Travis
----------------------------------------
Travis Dolence
Assistant Professor, Map/GIS Librarian
15 Hoskins Library
1401 Cumberland Ave.
University of Tennessee
Knoxville, TN 37996
Phone: 865-974-3878 Fax: 865-974-3925
Email: [log in to unmask]
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