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D-31 June 2002 3
Scanner—a device that electro-optically converts
a document into a series of pixels by detecting
and measuring the intensity of light reflected or
transmitted. When initially captured, each pixel is
a level of brightness (gray or color), initially an
analog quantity, but potentially digitized.
NOTE:For many applications, total information
about each pixel is not needed and would
represent a burdensome amount of output
from the scanner. Therefore, most
scanners digitize the value of each pixel
and reduce the amount of data output to
only that which is required. For example,
output might be limited to one bit per pixel
for “black-and-white” scanning.
Scanner threshold—the brightness level above
which a pixel is considered pure white and
below which the pixel is considered pure black
(sometimes set manually [lighter/darker
setting], or set automatically based on the
average brightness of the document).
Record Classification
On the basis of required retention, photographic
records can be classified broadly as requiring
medium-term storage and long-term storage.
Archival medium—recording material that can
be expected to retain information forever, so
that such information can be retrieved without
significant loss when properly stored. However,
there is no such material and it is not a term to be
used in American National Standard material or
system specifications.
Life expectancy (LE)—the length of time that
information is predicted to be retrievable in a
system at 21°C and 50% RH.
LE designation—the rating for the “life
expectancy” of recording materials and
associated retrieval systems.
NOTE:The number following the LE symbol is a
prediction of the minimum life expectancy,
in years, for which information can be
retrieved without significant loss when
stored at 21°C and 50% RH.
For example, LE-100 indicates that
information can be retrieved for at least
100 years of storage. Silver-gelatin films
have an LE of 500; thermally processed
silver (TPS) have an LE of 100 years.
Extended-term storage conditions—storage
conditions suitable for the preservation of
recorded information on the majority of freshly
processed photographic films for 500 years.
Medium-term storage conditions—storage
conditions suitable for the preservation of
recorded information for a minimum of 10 years.
Methylene blue—a chemical dye formed
during the testing of permanence of processed
microimages using the methylene-blue
method. Also called residual thiosulfate ion
and silver densitometric method.
Storage Hazards and Protection
There are a number of hazards to the satisfactory
storage of photographic film that apply to records
intended for medium-term, long-term, or
extended-term storage. In fact, it is not always
possible to predict the desired life of records at the
time they are made.
While films of medium-term, long-term, or
extended-term interest are subject to the same
hazards, the storage protection provided for
them will differ in degree because of a number
of factors. These include the cost of providing
storage facilities, desired record life, frequency
of record use, value of the records, etc. See
ANSI/PIMA IT9.11-1993
5
and ANSI IT9.2-1991.
6
Fire Protection
All Kodak Microfilms are slow-burning films as
defined by the American National Standards
Institute, Inc.
3
Even though photographic records
will burn considerably slower than paper, the
same precautions against damage by fire
should be taken for them as for paper records
of comparable value.
Depending on the importance of the records,
fire protection provided can vary from the full
protection described on the following pages for
valuable records to that provided by ordinary
office storage.