Median difference between Pristine-Gaia synthetic photometric metallicities and APOGEE/LAMOST spectroscopic metallicities as a function of the extinction values E(B − V) from the map of Schlegel et al. (1998, i.e., SFD) used to deredden the magnitudes. The samples are split in Galactic longitude to investigate spatial trends, with APOGEE having mostly stars in the inner Galaxy and the LAMOST sample covering two spatial regions: toward the inner Galaxy or the anticenter. The median distance of high extinction stars with E(B − V) > 0.2 in each sample are given in the legend. Error bars correspond to $\sigma /\sqrt{N}$, with σ the standard deviation between [Fe/H]_phot and [Fe/H]_spec in a given bin after clipping 3-sigma outliers, and N the number of stars in this bin.