Two representative examples of extinction as a function of distance (data from Green et al. 2019). Data points mark the assumed locations of the stars on the extinction curve, based on their distances; they do not imply extinction values. Distances are from Bailer-Jones et al. (2021). The turquoise circle represents the BeXB, the black circles show the field stars used for the ISM correction, and the blue circles correspond to other field stars. We also indicate the polarization degree (PD) of the field stars. The vertical dashed line marks the region of uncertain extinction.