Image reconstruction of the bright arc in SDSS J0004−0103, with n = 4, m = 9, and l_min = 3. Top-left: Lensed image cutout of the bright arc from the HST/WFC3 UVIS F390W observation. Top-middle: Model reconstruction. Top-right: Residuals after the model reconstruction is subtracted from the data. Bottom-left: Source model reconstruction with the white lines showing the Delaunay triangulation. The vertices of the triangulation are the positions after the points in the top-middle subplot are mapped onto the source plane using the lens model. Bottom-right: The source model reconstruction zoomed in showing high-magnification regions.