Effect of a change in mass-loss rate on the spectral classification. In each panel, the bottom black spectrum is the initial model, while the upper red one is the same model in which the mass-loss rate has been increased by a factor ~2.5 (only in the atmosphere model). The upper (middle, lower) panel corresponds to a model with an initial mass of 80 (40, 20) M_⊙. More information on the models is available in Table A.1. Shaded areas highlight the main luminosity-class diagnostic lines.