Abstract: A new class of photographic stabilizers is prepared and their use in photographic materials is disclosed. These compounds are 1-phenyl-3-pyrazolidinone derivatives corresponding to following general formula: ##STR1## wherein: A represents a group capable of adsorbing at the surface of silver halides;L is a divalent linking group and r is 0 or 1;R1 and R2 each represent hydrogen, lower alkyl or substituted lower alkyl.The photographic materials containing the substances of the invention are preferably DTR mono-sheet elements which after processing can serve as planographic printing plates.

Abstract: The present invention provides a method of preparing a planographic printing plate comprising the steps of:(1) exposing a DTR mono-sheet material containing a silver halide emulsion layer and a nuclei containing surface layer in a laser beam containing device, e.g. a helium-neon laser, an argon laser, or a semiconductor laser, wherein the said emulsion layer contains at least one emulsion showing following characteristics:(a) the emulsion consists principally of silver chloride but contains bromide ranging from 5 mole % to 40 mole % and iodide ranging from 0 to 1 mole %;(b) the emulsion belongs to the core-shell type wherein substantially all the bromide is concentrated in the core;(c) the emulsion grains contain Rhodium and/or Iridium dopants;(2) processing the DTR material by means of a developing or activator solution, containing at least an alkali agent and a silver halide complexing agent, followed by a neutralization solution.