action. The gelatin also acts as a sensitizer for the silver
In photographic films and papers, the main purpose
of the base is to support or hold the emulsion in place.
Depending on how the recorded image is to be used, the
base or support may be transparent or opaque. A
transparent base is used for transparencies viewed by
transmitted light and for negatives printed with
transmitted light. An opaque base is used for prints that
are viewed by reflected light.
The latest state of the art in light-sensitive materials
used in photography is the use of the electronic medium.
Still video disks do not contain an emulsion or a base.
When video mediums are used, light is converted to
electrical impulses, and these impulses are stored
magnetically on a tape or disk. Since it is the camera
itself that converts the light to electrical impulses, the
recording medium and all stages of the photographic
process can be carried out in normal room light.
The characteristics and use of black-and-white film
depends largely on the actual construction of the
emulsion. These characteristics include the following:
the degree of sensitivity to light, response to various
colors of light (color or spectral sensitivity), contrast,
exposure latitude, emulsion latitude, and emulsion
There are many types of black-and-white films
available. Each differs from others in one or more
characteristics. You should become acquainted with the
characteristics of films. This knowledge is helpful in
selecting the film most suitable for each photographic
Color Negative Film
A color negative film records a scene in image
densities opposite to the brightness of objects in the
scene, the same as a black-and-white negative film.
Color films can be recognized because they contain the
suffix color, such as Vericolor, Kodacolor and
Fujicolor. These color films are used when a print is the
final product. Most color negatives (except for color
film used for aerial photography) has an orange mask
incorporated init. This orange mask increases the color
separation which reproduces colors more accurately in
the final print.
During development, colors that are comple-
mentary to the color in the original scene are formed in
the emulsion. For example, a red object in the scene is
recorded as cyan in the negative. A combination of
yellow, magenta, and cyan record all the other colors
that we see in the scene. Color dyes in the emulsion
layers control the colors of light passing through the
To produce color prints or color transparencies, you
can print color negative film images on color positive
materials such as color paper and color print film. Color
negatives also can be printed on a special panchromatic
black-and-white paper to produce black-and-white
Amateur and Professional Color Films
Much of the color film used in the Navy is
manufactured by the 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.
They also have emulsions made up of many different
chemicals that tend to change slowly with time. 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
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 the 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.
The quantity of light can be measured in several
ways. The most accurate method is the use of exposure
meters. Photographic exposure meters are designed to
be sensitive to light in the same reamer as panchromatic
film. Therefore, an exposure meter reading can be
assumed to be valid under any visible lighting condition.
Several types of hand-held meters are available. Some