Minimum brightness temperature T_b, min and maximum brightness temperature T_b, max as a function of (u, v)-distance. The values were estimated from the visibilities following Lobanov (2015). The solid (dashed) lines show the average T_b, min (T_b, max) in bins of 10 Mλ for RadioAstron (black) and MOJAVE (red), while the points show the individual data values with the same colour scheme. The dashed horizontal lines show T_b calculated from Gaussian modelfits (see Table 1). T_b, min and T_b, max provide a reasonable bracketing for the brightness temperature at least for the RadioAstron data.