COLOR PROCESSING
Color adds realism to photographs. At one time
color was difficult to work with. It required special
cameras and specialized films that could be processed
only by the manufacturer of the film. Now, color
materials have been improved and are used extensively
in the Navy. They are far more popular than black and
white.
As discussed in chapter 2, color films have at least
three emulsion layers. Primary colors affect one
emulsion layer only, while complementary colors affect
two emulsion layers; for example, the color cyan affects
the blue and green sensitive layers. White light affects
all three emulsion layers. Black has no effect on any
layer. The type of process used depends on whether the
film is a negative type of film or a reversal (slide) film.
The most common processes used in the Navy are
Kodak Flexicolor for color negatives and Kodak
Process E-6 for color reversal films. The Eastman
Kodak Company continually strives to improve their
processes by making them more environmentally safe.
Always consult the Photo-Lab-Index for the most
current information concerning film and paper
processes.
COLOR NEGATIVE PROCESSING
In negative color film, the dye couplers produced
are complimentary to the primary colors of light;
therefore, a blue light records as yellow, a green light
records as magenta, and a red light records as cyan. All
colors within a scene are recorded through varying
combinations of these yellow, magenta, and cyan dyes.
The color negative is a halfway stage to a color print.
The cyan and magenta dye image layers formed by
color processing absorb some light wavelengths that
should be transmitted. In negative color film, these
absorbed wavelengths of light cause a color cast when
printed. To prevent this color shift, the manufacturer has
given the green and red sensitive emulsion layers a
yellowish and pinkish tint, respectively, during
manufacturing. These tints are what form the overall
orange mask that you see in finished color negatives.
Some color film used for aerial photography does not
have this orange mask. This allows for a direct
interpretation of the negative image. An orange-
masking filter is added when these films are printed.
The Kodak Flexicolor process is used for
processing color negative films and some monochrome
film, such as Ilford XP2. There are four chemical steps
and two wash cycles in the Flexicolor process. They are
as follows: color developer, bleach, wash, fix, wash, and
stabilizer.
Color Developer
The first step in color negative processing is color
development. A color developer in color processes
works nearly the same as a black-and-white developer.
The exposed silver is developed by a developing agent
and converted to metallic silver and by-products are
released. As the color developer is working at
developing the silver, it becomes oxidized and reacts
with nearby dye couplers. Dye couplers are built into the
emulsion around all of the metallic silver sites. The
primary function of a color developer is to develop the
exposed silver halide crystals to metallic silver and then
form dye around the metallic silver, using the oxidized
color developing agent.
Temperature of the color developer is the most
critical of all the processing steps. The temperature of
the color developer must be 100°F ±0.25°F (37.8°C
±0.15°C). All other wet steps in the process can be
within the range of 75°F to 105°F (24°C to 41°C);
however, it is best to maintain all solutions at constant
temperatures.
Bleach
Bleach is found in all color processes. The purpose
of the bleach is to take the metallic silver still in the color
film (or paper) and convert it to a form that can be fixed.
In color products, all of the silver must be removed.
Only the color dyes form the image. The bleach
chemically converts the silver metal back to a soluble
silver halide.
Fixer
The function of fixer is the same in color processes
as it is in black-and-white processes. A fixer converts
the silver halide to a water soluble form. Most fixers use
thiosulfate as the fixing agent in an acidic solution.
When fixing is incomplete, unwanted silver remains in
the image. This causes a loss in contrast, added density,
and an unwanted color cast.
Stabilizer
The final wet step in color negative film processing
is the stabilizer. The main purpose of this solution is to
provide a wetting agent to prevent spotting of the film
and to prevent unused magenta dye couplers from
attacking the newly formed magenta dye.
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