A photohardenable composition comprising an addition polymerizable or crosslinkable material, a photoinitiator composition capable of initiating polymerization or crosslinking of said polymerizable or crosslinkable material, and a compound of the formula ##STR1## wherein Q represents --C.dbd.O or --C--OH; X represents S or N which is unsubstituted or substituted with alkyl or aryl groups;R.sub.1 represents H, alkyl, aryl, alkoxy, bezoyl, arloxy, acyl or monosubstituted amino groups; andR.sub.2 represents H, alkyl or aryl groups is disclosed. The composition is preferably contained in microcapsules and is used in photosensitive imaging systems. The five member aromatic group containing the imine moiety functions to reduce the likelihood of short time scale reciprocity failure of the composition and enable imaging using high intensity radiation sources. An imaging method using the inventive composition is also disclosed.