Digital Noise Reduction: Where'd That Cartoon Go?: "As film is output to tape, DVNR's algorithms are designed to compare frames in the same scene and pick out unwanted noise such as grain, dirt and scratches. Once picked out, the system selectively replaces the unwanted parts of the image with parts from the previous and subsequent frames. The system's level of intensity is controllable thereby making it more or less sensitive to the noise on screen. Certain complications arise however when DVNR is used with animation. In animation, DVNR easily confuses the high contrasts and thin black lines commonly found in cartoons, and mistakes them for dirt".