Dye coupling is a chemical process in colour photography in which the by-products of colour development react with colour couplers embedded in the film or paper to form dyes. These dyes combine to produce the final coloured image.
This process is fundamental to modern colour films and papers, allowing accurate reproduction of colours through controlled chemical reactions during development. Understanding dye coupling helps photographers and technicians appreciate how colours are formed, maintained, and can be manipulated in photographic emulsions.