Profiles and bisectors averaged over pixels with similar atmospheric properties. We show data from synthetic spectra taking all isotopes into account (orange) and taking only the most abundant isotope (green) into account. Top row (panels a, b, and c): Results computed from a selection of strong (solid lines) and weak (dashed lines) magnetic fields in the formation height region of the line core (see text for details). Bottom row (panels d, e, and f): Only profiles and bisectors over the pixels harboring upflows (solid lines) or downflows (dashed lines) in the formation height region of the line core (see text). The bisectors are shown on an absolute wavelength scale (panels b and e) and on a scale where the bisectors are centered on the line profile minimum wavelength (λ_min). The synthetic data correspond to snapshot muram_en_518000_503s.