The light stability of organic substrate materials such as photographic dyes is improved by the copresence of at least one of the complexes shown by following formulae I, II, III, or IV ##STR1## wherein M represents Cu, Co, Ni, Pd or Pt; R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each represents a hydrogen atom, a halogen atom, a cyano group or an alkyl group, an aryl group, a cycloalkyl group or a heterocyclic group bonded directly or through a divalent connecting group to the carbon atom of a benzene ring; or R.sup.1 and R.sup.2 ; R.sup.2 and R.sup.3 ; or R.sup.3 and R.sup.4 combine to represent the non-metallic atoms necessary to complete a 6-membered ring; R.sup.5 and R.sup.8 each represents a hydrogen atom, an alkyl group, or an aryl group; R.sup.6 represents a hydrogen atom, an alkyl group, an aryl group, or a hydroxyl group; R.sup.7 represents an alkyl group or an aryl group; and Z represents the non-metallic atoms necessary to complete a 5-membered or 6-membered ring.