Tone reproduction curves for calibrating a marking system are obtained using a test pattern with a plurality of patches, preferably a plurality of first test patches extending in a first direction and at least one second test patch extending in a second direction crossing the first direction. Reflectance values are obtained from the first and second test patches. A set of gray balanced tone reproduction curves are obtained based on the reflectance values of the first test patches, and a set of spatial gray balanced tone reproduction curves are obtained based on the reflectance values of the second test patches.