1. A method for adjusting color balance for an image, comprising: capturing a plurality of calibration images of a calibration target, wherein the calibration target includes a color reference region illuminated by a light source having a distribution of frequencies that cycles over a fixed time period, wherein the calibration images are captured over a calibration period that is greater than or equal to the fixed time period, wherein each of the plurality of calibration images is associated to a time identifier; and calculating a color balance adjustment for the plurality of calibration images, for forming a time-dependent color spectrum model of the color balance adjustments, wherein the color spectrum model models changes in the light source over the fixed time period.