Dyestuff diffusion transfer process - using colourless non-diffusing cpd. with coupler gp. in emulsion

The material used contains a non-diffusing cpd. (I) of formula A-SP-NH-so2-B in the Ag halide emulsion or an adjacent binder coat (in which one of A and B (pref. A) is a gp. imparting diffusion fastness and other (prf. b) is a colour coupler gp. bound to the mol. via a non-coupling postion; SP is a grouping eliminated by developer oxidn. prods., of formula X is =O, =S or =NR, R being H or alkyl; Y is a bond or bridging member, e.g. -O-, -S-, -NR-, -CO-, -SO2-, -SO2NH-, -CO-NH- or , opt. substd.; Z is a bond between Y and C or together with C and X forms a 5- or 6-membered heterocycle in which X is N; R1 is H, (1-20)C alkyl, aralkyl, aryl or alkyl- or aryl-substd. amino, in which 2 alkyl gps. on N can be closed to a ring; R2 is as R1 or an acyl gp, derived from a (1-20)C aliphatic or aromatic carboxylic acid; R1 and R2 together can complete a (5- or 6-membered) carbo- or hetero-cycle, opt. with anellated benzene ring; R1 and/or R2 has an A substit.). (I) are colourless, diffusion-fast, colour yielding cpds., which make satisfactory development and dyestuff transfer possible.