Redox dye releasers o-sulfonamidophenol

A photographic unit for a color diffusion transfer process comprising a support, a photosensitive element, an image-receiving element, and an aqueous and alkaline liquid processing composition, said photosensitive element comprising at least one silver halide emulsion layer having associated therewith a dye releasing redox compound represented by the general formula ##STR11## wherein G represents a hydroxyl group or a group giving a hydroxyl group upon hydrolysis,

• Col represents a dye or a group giving a dye, both being diffusible when released upon hydrolysis;
• R represents an alkyl group or an aromatic group,
• X represents an electron donating group substituent when n is 1, or substituents, which may be the same or different, one of said substituents being an electron donating group and the second or second and third substituents being selected from the group consisting of an electron donating group or a halogen atom, wherein X groups may form a condensed ring, excluding an aromatic ring, with each other or with OR,
• n is 1, 2 or 3 and the total carbon number of X.sub.n and R is larger than 8.