An apparatus capable of real-time processing of video signals has been implemented for the purpose of measuring image activity in television programs. The basis of the system is a digital preprocessor that yields data sets which describe the difference between selected fields of an input video signal. Subsequent computer reduction and analysis of the data provides measures of activity such as the frame difference signal and spatial correlation. The results of a series of experimental trials using typical broadcast television are presented, and suggest that image activity is separable into two categories: one caused by movement of the image within the frame, and the other by scene switches.