Just as phototiming enhances the usefulness of spot-filming by eliminating exposure error, some means of assuring proper film density is a prerequisite for the broader clinical application of cineradiography. In the past, manual control of milliamperage by a millivolt monitor of the image tube current (Philips Co.) and a pre-read microammeter measuring the phototube current of a brightness-stabilizing circuit (Westinghouse) were used to establish correct cine film exposures in this work. Later, improved brightness stabilizers were employed in an attempt to maintain constant light levels for recording anatomical areas of varying opacity. While these devices, if properly used, permit one to achieve satisfactory film exposures, they are tedious to adjust, and the task of obtaining reproducible results under all conditions of cine operation requires a rather complicated procedure on the part of the radiologist. There is need for a simple-to-operate device which will assure constant film density at all film sp...