1. An automated, computerized method for manipulating an image, comprising the steps of: a computer executing the following steps: providing an image file depicting an image; deriving a bi-illuminant dichromatic reflection model representation of correct color of material depicted in the image, to represent correct color values for the image, across multiple materials of the image, within a range extending from fully shaded color value to fully lit color value, the bi-illuminant dichromatic reflection model representation of correct color being expressed by a characteristic spectral ratio consistent across multiple materials of the image wherein the characteristic spectral ratio is calculated as a ratio between a bright color and a dark color, each of the bright color and the dark color being a multi-band representation of a single material in the image, to provide an indication of correct color change, from fully shaded color value to fully lit color value, across multiple materials of the image; and utilizing the bi-illuminant dichromatic reflection model representation to manipulate the image of the image file to generate a manipulated image having correct color of material depicted in the image, the correct color being set at any selected degree of adjustment within the range extending from fully shaded color value to fully lit color value and determined as a function of the correct color values represented by the characteristic spectral ratio expression of the bi-illuminant dichromatic reflection model.