G-band variability amplitude (va_G) of all Gaia DR2 sources with G <  13 mag, excluding those with known variability flags and with RUWE > 1.4, as a function of G magnitude. All objects at G <  8.5 mag but only every 50th object at G >  8.5 mag are plotted as black dots for clarity. Overplotted cyan symbols and error bars show the simple mean values and standard deviations in 0.1 mag wide intervals, whereas red symbols and their error bars show the corresponding results from Gaussian fits.