Area above a given magnification for a single halo at z_l = 0.4 with mass 2 × 10¹⁵ M_⊙ and for a source at redshift z_s = 4. The area computed in the image plane does not follow the μ⁻² law at low and moderate magnifications ( μ <  40). At very high magnifications ( μ >  150), resolution effects break the μ⁻² law, but the area can be safely extrapolated to high values of the magnification above μ ≈ 50.