Comparison of absolute J magnitudes derived using either YY, Dartmouth, or Padova isochrone sets. Colors label an average dispersion in magnitudes for non-peculiar spectra with S / N > 20 in a given (temperature, gravity) bin. Solar composition isochrones from the YY set with ages between 1 and 11 Gyr and with a 1 Gyr spacing are overlayed. Metal-poor isochrone sets would be shifted towards higher temperatures (see Fig. 2a).