Models for B1422+231. Top left: Ensemble‐average mass map, a miniature of which appears in Fig. 3. Top right: Mass map of a randomly chosen sample model from the ensemble; note the larger pixel‐to‐pixel variation. Bottom left: Lens potential for the galaxy in the sample model (external shear potential omitted); we see here how solving for the potential automatically smoothes out small‐scale fluctuations in the mass. Bottom right: Arrival‐time surface for the sample model; note that no spurious extra images are present.