Surface densities of QSOs at given magnitudes in the g-band from the BOSS catalog. The insert shows the celestial region we used to generate the plot, i.e., a region well away from the Galactic disk where the distribution is uniform. The two dotted lines show the QSO surface density for one square degree, which is found to be 19 and 0.76 when observing at a limited range of g = 20 and g = 18 mag, respectively. In the present context, we consider the bands g and G to be equivalent, although the effective wavelengths differ by about 100 nm. They vary greatly with spectral type, however, because both bands are very wide.