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 100F 0.25F (37.8C 0.15C). All other wet steps in the process can be within the range of 75F to 105F (24C to 41C); 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.

Unlike black-and-white film processing, color negative film cannot be push processed successfully; therefore, you must choose a film with an appropriate film speed for the lighting conditions in which you photograph your subject.