Comparison of a single spectrum from a temporally averaged and dark- and flatfield-corrected FISS-SP flatfield measurement with the FTS after convolution with the FISS-SP SPSF. The error curve is the square difference between the convoluted FTS and the measured profile. Vertical lines in the plot indicate magnetically very sensitive absorption lines with an effective Landé-factor (g∗) (Shenstone & Blair 1929) greater than 1.9.