DIR coupler

DIR couplers (DIR = D eveloper I nhibitor R eleasing) are substances which in the color film processing may be used.

When reacting with oxidized developer, they release a compound that migrates from more exposed areas to zones of lower exposure in order to slow down the development process there. This results in sharper edges between light and dark parts of the image by means of additional dye formation at the boundaries, which thus increases the impression of sharpness. Graininess and color brilliance are also decisively improved by this control process.