Magnitude differences between components of pairs, for different separation ranges. (a) Magnitude differences for pairs separated by more than 30 000 au (only due to fortuitous alignments). (b) and (c) Same distributions for pairs separated by 1000 < a_t < 2500 au and a_t < 1000 au (blue), distributions for the fortuitous alignments (orange), normalized according to the sample size, and the difference between the two distributions (green; i.e., the distribution of the magnitude difference for binary systems only). These histograms are sampled in 0.05 mag steps with one entry per star. In panel c, the number of fortuitous alignments is negligible, and thus the orange distribution is almost zero and green and blue distributions are superimposed.