1,201,396. Photographic materials. EASTMAN KODAK CO. Jan. 3, 1968 [Jan. 3, 1967 (3)], No.364/68. Heading G2C. Photographic materials, particularly silver halide emulsions and vacuum deposited silver halide layers, are sensitized by (i) a noble metal sensitizer and (ii) a labile Se compound formed by activating a non-labile Se compound. The non- labile Se compound may be activated by (i) treatment with a reducing agent, (ii) using a higher molar concentration of noble metal compound than Se compound, or (iii) heating the non-labile compound in the system after the latter has been sensitized by heating in the presence of the noble metal sensitizer. Specified non-labile compounds are KCN Se, H 2 SeO 3 and Co, Mn and Ni isoselenocyanate complexes. The reducing agents may be benzothiazolicon salts, mercaptans, disulphides, triphenylphosphine or a Pt or Au metal complex thereof, SnCl 2 , benzothiazoline and alkali-metal sulphites. The material preferably also comprises a water-soluble thiocyanate, a labile sulphur compound as stabilizer (e.g. a thiosulphate, a thiourea, thiosemicarbazide or a thiocarbamate) and conventional additives.