Lag–frequency spectra: the frequency and time units are expressed in natural units. The BH spin a = 0.8, and the reflection surface is cut at R_out = 1000 R_g in all cases. The shaded region is the low-frequency band used to calculate the energy-dependent lags in Section 3.2.2. (a) Comparison between the SE and thin disk cases (see labels for the configurations). h_LP is fixed at 10R_g. (b) Comparison between different h_LP for the SE disk.