1. A method for modeling the pixel elements of a dynamically varying color reproduction device from an output image pixels generated in response to a target test including steps of: producing an image with the device in response to an input signal from the test target wherein the test target comprises a plurality of pixels; measuring with a sensor an output signal representative of the output image corresponding to a target preselected color; and constructing a state-space model of color producing behavior for a single pixel including a matrix characterization of a gradient of change with respect to the input signal for the measured output signal