1.1 A. Film Speed
Description
This article is from the Gross
Specimen Photography, by Ed Uthman, MD
1.1 A. Film Speed
Film Speed, measured as arbitrary standardized units ("ISO" or, formerly, "ASA"). ISO and ASA are numerically equivalent units. The film speed depends on film manufacturing process and type of development used on the exposed film. Although films are packaged with a stated ISO rating, some may be "pushed" to higher speeds by special processing techniques. This should be kept in mind before throwing away valuable film you have mistakenly underexposed. The faster the film, the less the resolution (causing increased "graininess"); also colors are more subdued in fast film (such as Kodacolor 1000) than in "slow" film (such as Kodacolor 25). The graininess and subdued colors of very fast films can be used for artistic effect but are of no value in technical photography. Therefore, we tend to choose slower films for our gross lab cameras, so that we may produce pictures with the greatest resolution and most accurate color rendition. A film faster than ISO 160 should probably not be used.
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