Intensification

Reduction

Developed negatives that are slightly underexposed or underdeveloped may be corrected to a large degree by a chemical process called intensification. Intensification increases the density of a negative either by adding more silver to the existing silver deposits, or by depositing some other dense metal such as copper, mercury or chromium which combines with the existing silver to produce additional density. In other words, intensification is a process that builds up the density of the exposed areas of a film.

Since intensification processes have a softening effect on negative emulsions, it is imperative that films be hardened prior to treatment. If a hardener-fixing bath was used in processing the film to be intensified, this may be considered adequate.

Intensifier solutions are of two types:

a. Single solution b. Two Bath solutions, consisting of bleach and clear type.

Examples of single solution intensifiers are:

1. Silver intensifier (Kodak IN-5).

2. Mercuric chloride intensifier.

3. Chromium intensifier. (Be careful here, since both single and two-bath solutions are available.)

The most widely used two-bath intensifier (obtainable in prepackaged form) is Kodak's Chromium Intensifier.

Note: Intensification processes may be carried out under normal room illumination.

Negatives which are grossly underexposed cannot be corrected through intensification. Where no silver deposit is present, it follows logically that there is nothing to intensify!

Single solution intensifiers of the silver type provide a gradual and visible intensification which permit the user to stop intensification when the desired degree of density is obtained.

Two solution intensifiers of the chromium type permit the user to repeat the process if sufficient density has not been produced in the initial try.

There is some increase in graininess when this process is used, with Chromium Intensifier producing the least grain, while Mercuric Chloride intensifiers produce the most.

Reduction is used to improve negatives that are too dense or too contrasty, or both. The process of reduction consists of converting part of the silver image into a compound which can be dissolved.

Types Of Reducers.

1. Subtracting, or cutting, reducers which remove an equal amount of silver from all parts of negative, and which are most useful in treating negatives which have been overexposed.

2. Proportional reducers, which remove silver from the negative in direct proportion to the total amount. These reducers will remove, therefore, more silver from a highlight area than from a shadow area, thus lowering the contrast of the negative. They are especially useful in correcting negatives which have been developed to a higher contrast than desired.

3. Super-proportional reducers, which remove even a greater proportion of silver from the denser parts of a negative than from the thin parts, and are used to correct excessive contrast produced by overdevelopment of a contrasty subject. Since they remove so much more silver from dense areas than from the thin ones, they produce a marked lowering of negative contrast.

This has been a brief introduction of a few of the more common advanced techniques of development. Our intention in this text has been to give you an overview of what they are.

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