Abstract: This invention relates to a class of phthalein indicator dyes useful as optical filter agents in photographic processes to protect a selectively exposed photosensitive material from further exposure during processing in the presence of incident light. Such dyes comprise 3,3-disubstituted phthalides and 3,3-disubstituted naphthalides wherein the 3,3 substituents are p-hydroxy carbocyclic aryl radicals wherein one or both of the radicals possess a --CH.sub.2 --NRR' group ortho to the p-hydroxy group and the --CH.sub.2 --NRR' group(s) is capable of rendering the indicator dye substantially non-diffusible in aqueous solution.