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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photography, zoom, lense, exposure, aperture, bellow, composition, film speed, macro lense
