Total relative flux errors of the sources detected in the Ks- (upper frame) resp. H-band (lower frame). Only the 0° channel is shown here, but the error distribution is very similar in the other three channels. The values are based on variations between the fluxes measured for the same source at different dither positions. The red lines denote the 16/18 mag resp. 3/6% upper limits (see Appendix A).