Reconstructed dust continuum of SPT 0538−50. Top to bottom rows: Gradient, curvature, and area-weighted gradient regularisation types, all with the same colour scales. First column: Surface brightness (the area below 3σ significance has been masked, where σ accounts for the noise, artefacts in the data, and the non-linear effects of lensing); contours are in steps of 0.02 Jy arcsec², and the dashed grey lines show the tangential caustics. Second column: Magnification with signal-to-noise ratio contours in steps of 3σ. Third column: Effective magnification-corrected beam FWHM in the source plane with signal-to-noise ratio contours. Fourth column: Star formation rate surface density and caustics in grey. Ellipses in the bottom-left corner show three magnification-corrected beams in the source plane for $\overline{\mu }-{\sigma }_{\mu }$, $\overline{\mu }$, and $\overline{\mu }+{\sigma }_{\mu }$, where $\overline{\mu }$ is the mean and σ_μ is the standard deviation.