Sensitometric and spectroscopic techniques are used to characterize sensitizer centers produced by sulfur sensitization of AgBr octahedra. Sulfur sensitization primarily affects the long wavelength sensitivity in two spectral regions—around 550 nm and around 650–700 nm. The concentration dependence of the long wavelength sensitivity in these two regions shows the former to be associated with single-sulfide centers and the latter to be associated with double-sulfide centers. The achievement of maximum photographic speed is associated with the production of the double-sulfide centers. A prominent 495 nm peak is observed in diffuse reflectance spectroscopy of these emulsions that is not observed in the long wavelength sensitivity measurements. This peak is assigned to a product of the sulfur sensitization that is not photographically active.