A deflection transducer for dynamic studies in which the movable element has negligible inertia is described. The sensing element utilizes a light beam incident upon a photoconductive cell which is modulated by a suitably gridded film strip attached to the specimen at the desired location. The output of the photoconductive cell circuit is a varying voltage signal applied directly to a cathode ray oscilloscope. A calibration scheme is described and the results of tests are given. The data indicate agreement within 2% over the entire calibrated range of deflections.