Comparison of the PSF computed with the linearized approach and fully nonlinear approach for various values of σ_f for an unpolarized point source (left). Comparison of the radial polarization as a function of distance from the source position computed with the linearized approach and fully nonlinear approach for the same values of σ_f (center). Elongation of the PSF for a fully (100%) polarized point source computed with the linearized approach and fully nonlinear approach (right). In all cases, 𝒫_g(r) is given by the V11 PSF of ixpeobssim, and 𝒫_f is assumed to be a 1D Gaussian.