A method of monitoring one or more patches in an image-processing device comprised of photoreceptor, a controller, and a sensor, includes obtaining specular readings and diffuse readings from the one or more patches and computing values received from the readings. In addition, the one or more patches are from about 0.1 mm to equal or less than the field of view of the sensor where each patch size, location, and approximate value is known; and an analysis of variance (ANOVA) is automatically conducted from the known size, location, and approximate value of each patch.