The simple spatially variable PSF field used for the fiducial experiments in Sect. 7. In the left panel, the PSF ellipticity across the field is shown by arrows representing the (ε₁, ε₂)-components. The maximum ε_i component is 0.25. In the right panel, the corresponding PSF shape is shown as ellipses across the field. The size of the arrows and ellipse symbols is not to scale with the field coordinates.