Density of sources with photometric metallicities in the Pristine-Gaia synthetic catalogue (left-hand panel) and the DR1 catalogue (right-hand panel). The black contours are lines with E(B – V) = 0.15 and 0.5. By construction, regions with extinction E(B – V) > 0.5 are removed from the photometric metallicity catalogues and produce the white regions in the left-hand map. The impact of the Gaia scanning law on the S/N of the BP/RP information and, consequently, on that of the CaHK_syn magnitudes, is clearly visible; it is responsible for most of the irregular features in this map. The map of Pristine metallicities is more limited on the sky but also denser, owing to the higher S/N Pristine data: some stars with BP/RP information do not have high enough S/N to make it through the enforced SCaHK_syn < 0.1 cut but have a high-enough S/N in Pristine to generate a Pristine metallicity.