Differences between magnitudes obtained using different cameras for common galaxies (black dots) as a function of magnitude. The plots in the topmost row of the figure refer to the total magnitudes, while those in the remaining rows refer to the magnitudes within circular apertures of radii 2, 5, and 10 kpc, top to bottom. The plots in the rightmost column of the figure refer to the B-band, while those in the other columns refer to the U-band. The red dots in the plots of the topmost row of the figure (total magnitudes) refer to the stars. The green curves in the plots relative to the 5 kpc apertures (third row of the figure) illustrate the rms expected according to the formulas reported in the headers of the catalogs (see text for details).