Distribution of Δm, the difference between m_AUTO, the magnitude reported by SEXTRACTOR, and the input magnitude m_input for detected galaxies with 20 < m_AUTO < 24.5 for our baseline setup (solid black line; galaxies placed randomly). The distribution of ‘isolated’ galaxies (solid blue line) matches that of the grid-based results (red line), whereas the tail towards negative Δm matches that of ‘blended’ galaxies. The light grey dashed line shows that many of the objects flagged by SEXTRACTOR are indeed blends, but that many remain undetected. Blends even occur for objects that have no detected neighbour within 5″ (dashed blue line).