As plastics replace metal in automotive and other applications, aesthetic concerns due to scratch or mar damage replace rust and corrosion issues. This paper presents a novel method to quantify the visibility of a scratch on a polymer surface. It is shown that the most important factor is the optical contrast between the damaged area and its surroundings. The critical optical parameters that affect a viewer's perception of scratch severity are identified as the size and roughness of the scratch, and the color and gloss of the surroundings. An optical imaging system and method for measuring the optical parameters that result in this contrast is described.