Hα/Hβ flux ratio vs. the continuum flux at 5100 Å  in logarithm scale, for the five AGNs in our sample for which both Hα and Hβ fluxes are available (name denoted on each plot), and for a sample of 4800 SDSS AGNs from Shen et al. (2011; bottom right panel). The solid line represents the best fit of the observed data and the dashed line represents the typical ratio Hα/Hβ ≈ 3 expected in the case of pure photoionization.