Abstract: The present method includes moving a light reading head along the length of a color bar whose length lies in an X direction and simultaneously therewith moving said light reading head in a Y direction, where the Y direction is substantially orthogonal to said X direction. The method further involves keeping an account of the positions of said light reading head and noting, as a benchmark position, each time the light reading head passes in the Y direction from a position off the color bar to a position over the color bar. The method further involves computing a desired Y value for each of said benchmarks and a plurality of interpolated Y values linking adjacent desired Y values to form a track which (in a preferred embodiment) lies substantially along the middle of the color bar over which to guide said light reading head during a subsequent scan. The apparatus comprises a light reading head, with an aperture that projects a light spot which has a diameter of 1/2 mm, in a preferred embodiment.