An optical filter containing at least one naphtholactam derivative represented by general formula (I), wherein X is oxygen or sulfur; R1, R2, R3, R4, R5, R6, and Y are each hydrogen, halogen, nitro, cyano, aldehyde, carboxyl, hydroxyl, —NRR′, organosilyl, optionally substituted C1-C30 alkyl, optionally substituted C6-C30 aryl, or optionally substituted C7-C30 arylalkyl; and R and R′ are each hydrogen, optionally substituted C1-C30 alkyl, or optionally substituted C6-C30 aryl.