Functional relationships for the dependence of T_eff (left panels) and log g (right panels) on the photometric parameters Q (a ,b),  [u − b]  (c, d),  [c1]  (e) and β (f). Symbols correspond to the sample stars and curves are polynomial fits to the data for different luminosity classes, encoded according to the legend. A few stars have been excluded from the fits (crosses). Typical error bars are indicated. See the text for details.