This WSRT 21 cm image of the field around the bright radio source 3C 147 is virtually noise-limited, and has a dynamic range of 1.6 million. This dynamic range, achieved by de Bruyn et al. (2010, in prep.) using regular selfcal with the NEWSTAR package, is high enough to clearly show ring-like artifacts around moderately bright off-axis sources (see left inset) which are caused by DDEs. We used MeqTrees to apply differential gain solutions to the original data (with a sky model built up by de Bruyn et al. during their NEWSTAR reduction), which completely eliminated the artifacts (right inset).