Polymeric optical filter agents and photographic products and processes using same are disclosed. The polymeric optical filter agents are pH-sensitive optical filter agents comprising polymeric backbone units having the following hydrazone moiety: ##STR1## where R is a group which can provide a double bond for conjugation with the ##STR2## portion of the moiety to provide light-absorbing capability for the agent at a pH above its pKa, and X represents a substituent of R providing at least one electron-withdrawing group. The polymeric pH-sensitive optical filter agents have a highly colored light-absorbing form at a pH above the pKa and are substantially non-absorbing at a pH below the pKa. The polymeric optical filter agents are useful in photographic film units and processes for the protection of photoexposed photosenstive elements against the occurence of fogging during in-light development.