MIST isochrones (dashed black lines) in two different spaces: T_eff vs. log g (left) and T_eff vs. G (right), for an old metal-poor population (top), a 5 Gyr solar metallicity population (middle), and a young super-solar metallicity population (bottom). In each panel, three PARSEC isochrones with the same metallicity are plotted, one at equal age (grey solid line), one at τ − 20 per cent (blue solid line), and one at τ + 20 per cent (red solid line). Typical T_eff, log g, and G uncertainties (Q50) for giants (log g  <  3.5) and dwarfs (log g  >  3.5) for stars at [M/H] = [Fe/H] ± 0.2 dex are also plotted on the right side of each panel.