Intensity profile (in various energy bands) of a point source, with photon index = −2 simulated with the GEANT4, and assuming the V11 ixpeobssim PSF as input geometrical PSF, compared both with the V11 PSF itself, and with the intensity profile computed with our fiducial nonlinear formalism for two different values of the variance σ_f (upper-left). Comparison of the profile of radial polarization (in various energy bands between the same GEANT4 simulation and our fiducial nonlinear formalism, where the σ_f = 5 case has been multiplied by a factor of 2 (upper-right). The same as the above is shown in the lower panels, but for Cygnus X-1 as observed by the IXPE satellite.