Comparison of the ratio R of line to total opacity for conditions typical for the photosphere of a SN Ia at the thermalization optical depth which corresponds to an optical depth of  ≈ 2 to 3 in Thomson scattering for photons in the optical and near IR. Line opacity is given at 10 000 K and for a density of 10^-12 g cm^-3 for the Si-rich (top) and Fe-rich (bottom) composition (from Höflich 1993), corresponding to the thermalization and last scattering layers in subluminous and core-normal models, respectively. In the red (at  ≈ 7000 Å) the average R is higher by about 50% in the latter. The scattering optical depth at the last scattering radius is about 0.5 and 0.3 for subluminous and core-normal SNe Ia, respectively. As a consequence, continuum polarization will be smaller for the same degree of asphericity (see text). The dashed lines are the flux distributions for Planck functions of the corresponding effective temperature.