Abstract: The optical sensitization of 2- thiobenzimidazolylsulfonylimidate and meso-posi-tion ethyl substituted thiocarbocyanine dyes was studied. Electron Spin Resenance(ESR)and polarographic measurement of dyes and photographic emulsion tests show that efficiency of the supersensitizing combination is connected with ESR signal and polalographic half- wave poten-tial.When the oxidation potential of supersensitizer is below 0.88V,and lower than the oxidation potential of the sensitizer,the photographic sensitivity of this system is raised and so does the intensity of ESR signals. The function of supersensitization can be explained by the hole trapping mechanism.