Zoom on a 35″ × 35″ region in the V-band VST image of A151 and on the WINGS image, taken with the WFI camera at the MPG/ESO 2.2m telescope. The same contour levels are plotted in both images. Besides the slightly lower S/N of the VST image with respect to the MPG/ESO 2.2 m image, the shape and location of the contour is the same. This is an indication that the background subtraction did not alter the faintest structures in galaxy haloes.