Image-providing compounds for instant color photography are classified as positive- or negative-working according to their photographic functions, and as dye-releasing or- stopping to their image-providing mechanisms. Their characteristics and properties as functionalized dyes are discussed briefly. Several synthetic approaches to the compounds selected, e. g., dye developers, p-sulfonamidonaphthol and o-sulfonamidophenol dye-releasers, are reviewed.
