Abstract: A series of photographic properties including sensitivity, fog, spectral sensitivity, light absorption and Dember effect of AgBr(I) emulsions with different concentrations of calcium ions ([Ca²⁺]) has been mearsured for studying effects of calcium ions on chemical, and particularly on spectral sensitization. The results show that the sensitivities and fogs of emulsions are decreased with the increase of [Ca²⁺] at the same short digestion time. While the digestion limes of emulsions with even more [CaCa³⁺] were prolonged, their highest speed can be reached almost with the same value. The reason that the calcium ions retard the process of chemical sensitization at shorter digestion time and that the same highest speed with different [Ca²⁺] can be,obtained by prolonged digestion is due to the reaction of calcium ions with a part of AgS₂O₃^- (intermediate of sulfur sensitization) to produce less insoluble Ca(AgS₂O₃)₂ than Ag₂S.An information which has scarcely been reported was obtained by studying the spectral sensitization and Dember effect. As electron trap, calcium ions may inhibit spectral sensitization at long wavelength, and restrain intrinsic desensitization of AgX emulsion, because the adhering of calcium ions to the surface of AgX grains can prevent the intrinsic latent images from oxidization by dye holes.

Key words: silver halide emulsion, calcium ton, chemical and spectral sensitizations