An experiment was conducted to assess observer performance in a simulated air-to-ground target acquisition task. Terrain films depicting targets imbedded in rural scenery were presented by a closed-circuit video system which employed two methods of varying the image quality of the display. The effects produced by these methods, spot wobble and random or ‘white’ noise added to the video signal, were independently manipulated, photometrically measured, and included in the Modulation Transfer Function Area metric of image quality. Correlation with observer target acquisition data suggest that the predictive validity of the Modulation Transfer Function Area (MTFA) concept may be improved by the addition of a third function incorporating some portion of the power spectrum of the imaged scene. The facilitory effects produced by spot wobble and the deleterious effects of white noise on observer performance were also demonstrated.