Maps of two fBm images with different values of β. The fBms are shifted to positive values by adding an arbitrary constant, and they are normalized by their mean values. The maps have a resolution of 1000 × 1000 pixels. The inner fBm, residing within a circle with a radius of 300 pixels, has β = 2.4, and the outer fBm has β = 3.4. Top left subpanel: fiducial case, and middle and right top subpanels: cases in which the inner and outer fBms have been divided by a factor of 2 and 4, respectively. The lower subpanels display the corresponding Δ-variance spectra. The values of α = 0.4 and 1.4 are not fits to the spectra, but are shown as a reference to guide the eye.