Illustrative example for the estimation of the 70395 EW, EW_J0395, in WD 1529+428, a DZ with spectroscopic information from SDSS (left panel). Symbols are showing the J-PLUS photometry as in Fig. 1. The gray diamonds connected with a solid line in the right panel depict the best-fit solution to J-PLUS photometry but the J0395 passband, with the derived parameters and their uncertainties labeled: effective temperature (T_eff), surface gravity (log g) and parallax (ϖ). The white diamond represents the expected continuum flux in the 70395 filter in absence of polluting metals from the fitting process, see Eq. (7). The estimated 70395 EW is also presented in the panel.