Convergence metric as a function of iteration for the G-band Window Class 2 large-scale calibrations. The black line shows the L1 norm metric which compares the large-scale calibrations between two iterations. The last two points compare successive large-scale calibrations at the end of the initial set of iterations where the small-scale calibrations have also been carried out (see Carrasco et al. 2016 and Riello et al. 2018 for more details). The red line shows a modification of the metric where a default colour system has been used rather than a representative sample.