Abstract: A positive-working radiation-sensitive mixture is described that contains (a) a radiation-sensitive compound which forms a strong acid under the action of actinic radiation, (b) a compound with at least one C--O--C bond cleavable by acid, (c) a binder which is insoluble in water but soluble in aqueous-alkaline solutions, and (d) a polymethine dye. The polymethine dyes used are hemioxonol dyes or symmetrical cyanine dyes. In the light-sensitive mixture, these dyes effect high sensitization and high image sharpness contrast which, in addition, is substantially irreversible.