A method of modeling spectral characteristics of an input imaging device comprising includes adjusting digital values measured from a target to be linear relative to luminance of neutral patches of the target, for each channel of the input imaging device. The method further includes modifying the adjusted digital values to compensate for cross-channel interaction, for each channel of the input imaging device. In addition, the method includes converting the modified digital values to a spectrum, for each channel of the imaging device. An apparatus for modeling spectral characteristics of an input imaging device is also provided.