Imidomethyl blocked photographic reagents are useful in photographic elements, film units and processes. The blocked photographic reagents have the structure: ##STR1## wherein: J represents ##STR2## X represents the atoms to complete a 5- or 6-membered ring or ring system; R represents hydrogen, alkyl or 1 to 4 carbon atoms or aryl of 6 to 12 carbon atoms; andPR represents the residue of an organic photographic reagent containing a heteroatom through which it is joined to the imidomethyl blocking group.