Analysis of the 1532 duplicated measurements in the Landolt collection, for 679 stars. Each panel displays the paired magnitude differences in a different band. Solid lines are Gaussians centered on the mean difference µ and standard deviation equal to the MAD (median absolute deviation) of the paired differences σ_pairs. Dashed lines show Gaussians centered on µ and with a standard deviation obtained by summing in quadrature the Landolt uncertainties of the stars in each pair, σ_err. The ratios between the two standard deviations are annotated in each panel, along with relevant quantities.