1. A vehicular vision system, said vehicular vision system comprising: an image sensor operable to capture frames of image data; an image processor operable to process captured image data; wherein said image processor is operable to determine edges in captured image data; wherein said image processor is operable to determine a number of edges detected in individual frames of captured image data; and wherein said vision system adjusts a sensitivity of said image processor responsive to the determined number of edges detected in at least one frame of captured image data.