Predicted number of counts per spectral type bin a) and per apparent G mag b), in logarithmic units. The black line in the left panel corresponds to the derivation based on the relation between spectral type and I-band absolute magnitude included in Caballero et al. (2008), while the blue continuous line corresponds to the relation derived from the BT-Settl model family and the SLC calibration. The two horizontal (dashed) lines indicate the levels of predicted counts equal to one and ten. The right-hand side plot has been obtained assuming the relation between effective temperature and I-band absolute magnitude derived from the BT-Settl models and the SLC calibration.