We investigate the sensitivity of the colour-based quasar selection algorithm of the Sloan Digital Sky Survey (SDSS) to several key physical parameters of supermassive black holes (SMBHs), focusing on BH spin (a*) at the high BH-mass regime (MBH = 109 M?). We use a large grid of model spectral energy distribution (SED), assuming geometrically thin, optically thick accretion discs, and spanning a wide range of five physical parameters:
