Comparison of the Pristine-Gaia synthetic photometric metallicities with metallicities from high-resolution spectroscopy samples of metal-poor stars (Hansen et al. 2018; Sakari et al. 2018; Yong et al. 2021; Li et al. 2022; R > 25 000). In the left-hand panel, color traces the origin of the spectroscopic metallicities, as listed in the label. The photometric metallicities are of high enough quality that they track the spectroscopic metallicities down to the lowest metallicities available. In the right-hand panel, the color codes the temperatures of the same stars, showing that the agreement is generally better for cooler rather than hotter stars. In both panels, the dashed line corresponds to the 1-to-l line and the dotted lines represent offsets of 0.2 dex.