An image processor includes a Lee filter for processing image data to improve noise therefrom. The Lee filter includes a smoothing control signal. During filtering of the image data, the smoothing control signal is converted to a monochrome video signal that is provided to a display instead of, or in addition to, the filtered image data. The image projected by the display of the smoothing control signal highlights edge activity in the filtered image. This display of edge activity makes it easier to locate noisy areas in the image data and fine-tune the amount of filtering to further reduce noise present in the image data and yet leave the desired image details alone.