SEP measurements of λL_λ(1350 Å) continuum luminosity (top-left panel), C IV EW (top-right panel), C IV FWHM (bottom-left panel), and C IV-based SMBH mass (bottom-right panel) from simulated J-PAS sources. Blue dots, orange squares, and green triangles show the results for sources with 18 <  r <  20, 20 <  r <  21, and 21 <  r <  22, respectively, and dashed red lines indicate a one-to-one relation between actual and measured properties. The middle and bottom sub-panels display the mean and standard deviation of the logarithmic difference between actual and measured properties. We find that our method yields unbiased FWHM measurements only for lines broader than ≃1500 km s⁻¹ due to the limited spectral resolution of J-PAS photospectra, which prevents us from measuring the mass of sources with log(M_BH/M_⊙)≲8 in an unbiased fashion. We find similar results for Hβ and Mg II.