Appendix N Compensating Developers
Compensating developers are very dilute, slow-working developers that take advantage of the fact that denser areas of the negative (the highlights) exhaust developer at a faster rate than thinner areas. The reason is that the highlight areas contain more exposed silver.
As the film develops, residual byproducts (bromide ions) produced in the emulsion weaken the effect of the developer and slow the process. The function of agitation is to replace the weakened developer with fresh supplies. When the film is at rest between agitations in a compensating developer, the bromide ions build up at a much faster rate in the highlight densities of the emulsion than they do in the less dense shadow areas. This effect is ...
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