Using calibrated light sources, the sensitivities of several commonly used films have been determined in terms of the number of photons incident required to develop one grain of emulsion. By incorporating an image intensifier in the system, the time required to obtain an image of a given quality or information content can be reduced significantly. Criteria are discussed whereby an estimate of the time advantage can be made for various experimental conditions. Noise, quantum fluctuations, spatial resolution, and over-all detection efficiency are discussed.