Magnitude comparison between low- and high-resolution data. Red up- and left-triangles show multiple sources, green squares show individual sources, while blue squares shows multiple main sources. Top row: comparison of HST-ACS input and GALFIT-M output I-band magnitudes. Bottom row: same comparison as in top row, but instead of input high-resolution photometry we plot low-resolution HST-ACS-F814W photometry from OTELO catalogue. Lines represent the 25th and 75th percentile of the colour distribution per magnitude bin: light green dot-dashed – individual; dark red dashed – multiples; light blue dot-dashed – multiple main. See text for details on the samples selection (Sect. 4).