Calibration of the brightness transformations from M_V to M_G in Eq. (A.6) and vice versa in Eq. (A.7). Panel a: magnitude-magnitude diagram for the Hyades (red), the Pleiades (yellow), and the calibration by PM13 (blue). The same magnitude-magnitude diagram, but with switched axes, is shown in panel b. Overplotted are the found relation between the two magnitudes each. Panels c and d: residual between the calculated and measured magnitudes for both transformations each.