Preservation of Historical Records (1986) / Chapter Skim
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5. Photographic Film
5. Photographic Film
Pages 49-60
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From page 49... ...
Other technologies are applicable for producing the photographic image, but silver halide salts are by far the most used for recording black and white images. STRUCTURE The film's light-sensitive layer is called the photographic emulsion; it consists primarily of silver halide in a colloidal medium.
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From page 51... ...
Film supports are coated with various layers during manufacture to provide good adhesion with the photographic layer, to give static protection, or to eliminate light reflecting from the support surfaces back into the light-sensitive emulsion. The photographic emulsion is coated onto the plastic support from aqueous solutions.
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From page 52... ...
Any degradation of the cellulose nitrate base can release nitrogen dioxide, which has a devastating effect on the silver image {Carroll and Calhoun, 1955~. The chemical stability of cellulose triacetate and polyester supports and films has been studied using high-temperature aging results to predict lower tempera
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From page 53... ...
The stability of the photographic image depends on the emulsion type, and these types may include black-and-white, color, diazo, vesicular, and thermally processed silver. Of primary concern to the archivist are black-and-white images formed by silver halide.
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From page 54... ...
54 : ::< Eve .. PRESERVATION OF HISTORICAL RECORDS Mircofiln~ cabinets in National Archives microfilm reading room.
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From page 55... ...
Thermally processed silver films are also used in the micrographics industry. A silver salt on a long-chain fatty acid is the image-forming material, and after exposure to light a silver image developed by heat is obtained from the decomposed silver salt.
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From page 56... ...
In addition to these standards on film material, photographic processing, and storage, there are also the following standards on the formats used to make reduced photographic copies on microfilm and the required inspection and quality control: ANSI/NMA MS23-1983, Practice for Operational Procedures Inspection and Quality Control of First-Generation, Silver-Gelatin Microfilm of Documents; and ANSI/NMA MS14-1978, Specifications for 16 and 35-mm Microfilms in Roll Form. Great care has been taken to ensure that manufacturers, users, industry associations, and standards bureaus have all had appropriate input into these standards.
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From page 57... ...
Frequency of use of records 4. Needs or demand for distribution of information Economics and money available Equipment and manpower available The most economical format is roll film, particularly 16-mm when using a high-reduction filming.
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From page 58... ...
pages per exposure. bCine: Documents filmed with pages or frames arranged as in a motion picture film with the writing perpendicular to the edges of the film; Comie: Documents filmed with images running with top of the document at top of film and writing from left to right.
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From page 59... ...
1980. Predicting long-term dark storage dye stability characteristics of color photographic products from short-term tests.
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From page 60... ...
E: ~ ' - ~ :~ F~ :~: - ~: Magnetic tape storage area. Vast amounts of data can be preserved compactly by using magnetic recording media.
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