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 IT9.11-19935and 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.
