Left: distribution of the thermal source volumes obtained with the direct and indirect methods, V_dir (top) and V_ind (bottom), as derived from the optimum imaging algorithms individually selected for each event. Dashed lines indicate the median of the distributions. Also given is the number of measurements N. Right: comparison of V_dir and V_ind. Only cotemporal measurements are included. Error bars show the standard deviation from the different imaging methods. Also shown is a power-law fit (dashed line, with slope α), the rank correlation coefficient R, and the number of value pairs N. The dotted line denotes x = y. At the bottom of the plot, the mean ratio ⟨ V_dir/V_ind ⟩ is shown.