Metallicity distribution functions for the ks_thick disc (top panels) and the ks_thin disc (bottom panels) derived from our solution CMDs compared with those obtained from the spectroscopic surveys APOGEE (left), GALAH (middle), and the Golden Sample of Gaia-RVS (right). The red or blue curves correspond to the spectroscopic MDFs, and the black lines display the MDF distribution from each corresponding masked solution CMD (see text for details).