In the context of this article, analog image processing comprises methods to chemically control and improve image quality in color negative films during photographic processing. The chemical control applies to the generation of image dyes and to the optical interaction of partial dye images. The image dyes are generated in two consecutive steps: silver reaction and coupling reaction. Yield- and distribution-parameters of these reaction steps are relevant for image-quality aspects. In this review the various chemical methods to achieve image processing (e. g. inhibition, (dye-) amplification, dye spread) are discussed.
Joachim Lohmann, Johannes Willsau, "Analog Image Processing in Modern Color Photography" in Journal of Imaging Science and Technology, 1999, pp 550 - 559, https://doi.org/10.2352/J.ImagingSci.Technol.1999.43.6.art00011