(I, V − I) colour–magnitude diagrams of the Sculptor dSph for increasing elliptical radius. Error bars show the average photometric error at that level. The 50% completeness level for this subsample is indicated by the (red) solid line. the blue line shows a reference isochrone ([Fe/H]  =  −1.80, [α/Fe] = 0.2, age = 11 Gyr) which runs through the middle of the RGB in the centre.