a) Filled black circles mark the spectroscopic values, open circles microlensing values. Dash-dotted blue line show the Casagrande et al. (2010)T_eff-colour transformation, dashed green lines the Green et al. (1987) transformation (for three different log g), and the solid red lines the Lejeune et al. (1998) transformation (for three different log g). b) Differences between Casagrande et al. (2010) and Lejeune et al. (1998). c) Differences between Green et al. (1987) and Lejeune et al. (1998). The markers in b) and c) show the differences that should be applied to the microlensed dwarfs if the Casagrande et al. (2010) and Green et al. (1987) trandformations had been applied instead of the one from Lejeune et al. (1998).