Comparison between the mean SED of RC stars in the different sub-fields using the IB data after the basic calibration (blue points) and after applying the local calibration (red points). The SEDs are shifted in magnitude to achieve overlap. The effect of the local calibration is more important in the outer regions. The size of each sub-field is around 8.6″ x 8.6″. The panels corresponding to the different sub-fields overlap with the specific sub-field in the background image.