that averages approximately 5400 K. Tungsten films are
balanced for use with illumination of 3200 K without
filtration.
The Kelvin temperature of the exposing light for
reversal films is much more critical than the color of the
exposing light for color negative films. When an
exposing light is used other than that for which color
negative film is balanced, adjustments to the filter pack
can be made during printing to achieve proper color
balance. With color reversal film, however, a slide is
usually the final product. When the color of the exposing
light is other than that for which the film is balanced, the
transparencies are off-color. You should strive to expose
all color films with the color light for which the films
are balanced.
Although color films have three separate emulsions,
only one ISO film speed is assigned. An ISO film speed
for color film is most accurate when the illumination
used is the one for which the film is balanced.
Amateur and Professional Color Films
Much of the color film used in the Navy is
manufactured by Eastman Kodak Company. Kodak
markets color films for both professional and amateur
photographers. Color films intended for use primarily
by professionals are identified by the word professional
in the name; for example, Kodak Vericolor III
Professional Film, Type S (VPS).
Both professional and amateur films have similar
color quality, sharpness, and granularity characteristics.
Also, they have emulsions made up of many different
chemicals that tend to change slowly with time. Starting
from the day they are made, all color films begin to
change; and as the films age, their color balance
changes.
Amateur films are manufactured to age and reach a
peak color balance much later than professional films.
The manufacturer allows for the time amateur film will
be in storage, on the store shelf, and in the camera before
it is developed. The ISO speed assigned is adequate for
calculating exposure for normal picture-taking
situations.
Professional films are manufactured so they are
very near their optimum color balance at the time they
are shipped from the factory. These films should be kept
refrigerated or frozen until shortly before use.
Refrigeration keeps film near the optimum point until
used and provides the photographer with confidence in
consistent results. Precise film speeds are provided for
professional films. The film is intended for prompt
processing to prevent any significant shift in color
balance after exposure.
If you require optimum color balance and precise
film speed within about 1/6 f/stop professional film is
appropriate for your work; however, when you intend to
be away from home base for an extended period of time
without refrigerated storage or processing facilities,
amateur film should be your choice.
Instant Picture Film
Currently, the only manufacturer of instant picture
film is Polaroid. There are two basic types of instant
picture film: peel apart and integral. After exposure and
removal from the camera, peel-apart film must be timed
while the film develops. After it has developed for the
specified period of time, the negative backing is peeled
away and discarded. Integral films develop outside the
camera and have no negative backing to be removed.
Instant picture color films are tripack materials with
built-in processing. Peel-apart film uses a system
whereby the exposed silver halides develop to a metallic
silver negative. When no metallic silver is present, dyes
pass to form the color image. Integral films use a
reversal process in which the areas of unexposed silver
halides are the locations where the dyes are produced to
form the positive image.
Instant picture film is a very useful medium in an
imaging facility, particularly when still electronic
technology is not available. Instant picture film is used
commonly for identification and passport photographs,
but it is also valuable in determining test exposures.
Before you make your final exposures on conventional
film, a Polaroid photograph can be taken to confirm
composition, lighting, and exposure.
FILM SIZES
There are two types of film formats used commonly
in photography. They are roll film and sheet film. Both
formats come in a variety of sizes.
Roll Film
All roll film is packaged so the film can be loaded
and unloaded from a camera in daylight. Number 120
film has a paper backing that prevents the film from
being exposed in daylight; 35mm film is wound in a
lighttight cassette that prevents the film from being
exposed by ambient light.
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