Mean lens model among the best-fit posterior samples for our fiducial “Cluster+Shear” model. First row, from left to right: color image of the data, color image of the model with reduced χ² from image residuals (which differs from the full log-likelihood, see Eq. (3)), convergence map (with convergence and surface brightness contours), and color image of the unlensed source model. Remaining rows, from left to right: data in the indicated filter, model, normalized residuals (areas excluded from the fit appear white), unlensed source model, S/N source map defined as the mean source model divided by the standard deviation of the model posterior in each source pixel. Critical lines and caustics are indicated in some of the panels as white solid line in the image model panel, and dotted lines in the right column panels. The source S/N is higher within and along the caustics, since image multiplicity and lensing magnification are higher, respectively.