Comparison of GSP-Spec and literature metallicities. Top: 2D histogram of the differences between the GSP-Spec metallicities and the literature values as a function of uncalibrated log(g) for our best-quality sample. The red full line is the running mean of the difference, and the dashed line is the fit to the running mean, defining the correction to apply. Bottom: medium-quality sample showing the differences between the calibrated metallicities and the literature values.