Example of the effect of luminosity in early-G stars. The stars are shown from bottom to top: HD 74395 (G1 Ib) and HD 84441 (G1 II). Vertical lines indicate the position of spectral features useful for classification. Their colours represent the dominant chemical species in each feature: red for Mg I (the Mg Triplet), blue for Fe I, green for Ti I and Mn I, yellow for other atomic lines (Ca I, Cr I, V I and II, and blends), cyan for Balmer’s H lines, and magenta for the TiO bands (see text for details).