Radial dependence of the axis ratio ϵ. In the unperturbed case the isodensity contours are circular, i.e., . The SPTed mass distribution shows for radii deviations of up to 5% from circularity, whereas for larger radii the deviations can be up to 20%. The convergence map for f₂ = −0.55 and γ_p = 0.1 does not show concentric isodensity contours for radii larger than 1.3 θ_E and therefore no ellipticity as a function radius can be determined.