Expected normalized distributions of the distances for the lensed sources – when taking into account the EROS microlensing detection efficiencies – (thin lines) and of the lenses (thick lines) from the simulation of our simple model (upper) and the Besançon model (lower). The sparsely-populated distributions around 4 kpc (for β Sct and γ Sct) correspond to the contribution of the bar objects. The dashed curves show, as a function of the distance, the average extinctions of the stars in the simulated EROS-like catalog (in V magnitude, on the right scale). It is strongly biased in favor of small extinctions mainly due to the magnitude selection I< 18.4.