Left panel: luminosity ratio R as a function of the BH spin for different torus aperture angles (θ_T = 30° −45° −60°) and for θ_v = 30° (no solution is shown for θ_T < θ_v). The dashed black line is the KERRBB limit (θ_v = θ_T = 0°). In the SS case, the ratios (not shown for clarity) are R = 0.43 − 0.29 − 0.14 for θ_T = 30° −45° −60°, respectively (see right panel). The small plot is a zoom onto the a > 0.7 region. Right panel: luminosity ratio R as a function of the torus aperture angle θ_T, for different spin values (a = −1, 0.9, 0.9982) and viewing angles (θ_v = 0° −30°). The a = 0 case is similar to the one with a = −1. All solutions lie between the two extreme spin curves (a = −1, 0.9982). For comparison, the red curves represent the SS results. In both plots, the curves are calculated using Eq. (2).