A photosensitive composition comprising, (A) an oligomer or polymer containing at least one carboxylic acid group in the molecule and having a molecular weight of 200'000 or less; (B) at least one photoinitiator compound of formula I ##STR00001## wherein R.sub.1 is linear or branched C.sub.1 C.sub.12alkyl; R.sub.2 is linear or branched C.sub.1 C.sub.4alkyl; R.sub.3 and R.sub.4 independently of one another are linear or branched C.sub.1 C.sub.8alkyl; and (C) a monomeric, oligomeric or polymeric compound having at least one olefinic double bond, is especially suitable for preparting photoresists, in particular color filters.