S/N = 5. Measured maximum gradient versus mean gradient for efBm maps with spectral indexes ζ = 2.5,3,3.5 (full line, dotted, and dashed lines, respectively) and different inverse brightness contrasts W = 0.1,0.25,0.5,1,1.5,1.75,1.9. The error bars indicate the standard deviation of the ensemble of ten different random realizations and seven different enhancement scales. The long-dashed line is the identity representing straight spectra, i.e. g_max = ⟨ g ⟩. The dash-dotted line represents the lower limit of g_max as a function of ⟨ g ⟩ below which the scale of the peak cannot be reliably determined (see Eq. (38)).