From a careful evaluation of a very simple hologram, the photographically produced grating, we have been able to obtain quantitative data on image reconstruction efficiency as a function of processing procedures and illumination parameters such as orientation angle and wavelength. Experimental results are presented which show the dependence of efficiency on exposure, both before and after bleaching of the emulsion layer. In addition, the orientation sensitivity of thick-emulsion holograms is studied, and it is shown that maximum diffracted power occurs when the Bragg reflection condition is satisfied.