The PCA-based host-galaxy subtraction for the highly contaminated ID 12907 (SN 2006fv) at z  =  0.132. Left panel: the observed spectrum (black) is plotted together with the best fit (light grey). The galaxy template of the best fit is shown as a dotted line. The grey line shows the SN spectrum after subtraction of the estimated galaxy light. Right panel: the (host subtracted) SN spectrum is shown with and without correction for the wavelength dependent flux loss described by s (black/grey). The host galaxy contamination estimated from photometry (80%) agrees well with the fraction of host galaxy light indicated by the subtraction. The expected differential slit loss, see Sect. 5 (30% at 4000 Å) also seems compatible to what the best fit in the host-galaxy subtraction indicates (compare the curves at 4000 Å in the right panel).