A high-definition, or compensating, developer adds increased sharpness to the image by enhancing contrast of image edges and fine detail in the negative. High-definition developers may increase film speed by one or two f/stops, but they also increase graininess. High-definition developers are recommended for use only with fine-grain (slow or medium speed) films.

Some of the high-definition developers are as follows:

Acufine

Ethol TEC

You should consult the film data sheets or the Photo-Lab-Index for the recommended developers for each particular type of film to be processed.

CHANGES IN DEVELOPER WITH USE

The function of a developer is to change chemically the sensitized material treated in it. It stands to reason then that a chemical change also takes place to the developer itself. Most developers are used more than once. Therefore, you must know what changes to the developer can be expected and what can be done to prevent them or at least compensate for them. The primary changes that occur to a developer as it is used are as follows:

Some developer is removed or carried out with the film and on the film hangers or reels.

The developing agents are used up by reduction of silver halides to black metallic silver and by aerial oxidation. When the developing agents are used up by the reduction of silver halides, the by-products of the reaction cause the pH of the solution to drop, thus becoming more acid. When the developer agents are used up by oxidation, the pH tends to rise.

The preservative is used up, thus the developing agents oxidize faster.

The bromide within the solution is increased because the bromide is released from the film emulsion itself.

The effects of these changes to a developer are as follows:

The development time required to reach a given contrast index or gamma is increased. Therefore, when a developer is used over and over, development time must be increased as more film is developed.

The effective film speed produced by the developer decreases because of the increased bromide (a restrainer) in solution. However, this speed loss may be partially offset by increasing development time to maintain image contrast.

Complete exhaustion of a developer occurs when the developing agents are all used up. The approach of exhaustion is characterized by a brown color of the solution. Since a developer in this state can stain sensitized materials, it should not be used.

In most Navy imaging facilities, it is not economical to use a developer to the practical exhaustion point and then discard it. The quality of the image usually suffers

long before the exhaustion point of the developer is reached. Replenishers are usually used to prevent this from happening.

Replenishment of a developer involves replacing those chemicals in the used developer that are exhausted by a replenisher so that the developer remains consistent. The aim of replenishment is not to keep the composition of the developer constant but to keep its activity constant.

There are two commonly used methods of replenishment. The first or topping off method is used extensively in tank processing. When topping off is used, the developer solution is maintained at a constant level in the tank by adding replenisher, so the volume added is equal to the amount of developer carried out. When you are replenishing by this method, it is possible to maintain consistency in development for only a certain period of time. After a given volume of replenisher has been added to the developer, the developer must be discarded. This procedure is then repeated with new developer.

The second replenishment method is called the "bleed" method. The bleed method is used primarily with machine processing where a circulating developer system is used. In the bleed method, used developer is drained off and replenisher (in proportion to the amount of film processed) is fed in, so the characteristics and the level of the developer in the machine remain constant.