Probability of magnification in the source plane. The black solid line shows the probability of the total magnification when microlenses are present. The black dot-dashed line shows the probability computed in the same area, but when microlenses are not included (i.e., the smooth model). The black dotted line is the μ⁻³ law expected for smooth caustics. The blue dotted and red dashed curves are the probability of magnification from the regions with positive and negative parity, respectively.