Contour plot of the radio source L0412 before (left) and after (right) multi-source self-calibration has been applied. Contours are drawn at 0.1 mJy × (1, 2, 4, ...). The S/N was improved from 72 to 115. The peak flux density has increased significantly, the noise has dropped, and image artefacts are much reduced. At low elevation, or when calibration is poorer, these effects will be more pronounced.