Results of the second artificial-star set of tests. Left panel shows the color–magnitude distribution of the artificial stars inserted into the image section as described in Sect. 5. The stars are taken from the NGC 5128 halo field measured by Rejkuba et al. (2005), shifted to the distance and reddening of M 87. Middle panel shows the stars from the left panel that were actually found and measured on both frames; and the right panel shows the measured photometry for the stars that were recovered.