Sketch of the method followed to unveil the artificial shear arising due to truncation of the κ map: mock lens system (left) created with a pure NIE κ map truncated with a circular mask of diameter 40″ – i.e. corresponding to a truncation radius of 10 × θ_E – and modelled (middle) using an NIE profile (upper) and NIE+shear (bottom) with associated residuals expressed in the percentage of the input flux (right).