BP and RP flux-over-error ratios for 39 873 sources in a 50 pc sample retained by Eq. (A.3). The vast majority of objects is located below the 1:1 line (blue dashed line); i.e. the S/N for these objects is higher in the RP band than in the BP band. Grey lines correspond to the S/N threshold applied in Eq. (B.2). It is noteworthy that there is a significant fraction of objects with high-S/N RP photometry, but low- S/N BP photometry (S/N_BP < 20 & S/N_RP > 20).