Stokes profiles of Fe 1564.85 nm (blue), Fe 1565.29 nm (green) and Fe 1566.20 nm (red) recorded with FTS and GRIS. Top row from left to right: Stokes I recorded with the FTS for the QS, a warm umbra and a medium warm umbra. Other rows from top to bottom: Stokes I normalized to the average QS, and Stokes Q, U and V in percent of the average continuum intensity. From left to right: Stokes vector from the QS, penumbra, umbra, and a region where the Stokes V profile shows three lobes. The Fe 1565.29 nm line is strongly blended by a hydroxyl radical line pair in the umbral example. The spectral regions used to estimate the noise in the polarimetric component are gray shaded in the lower left panel. The signal in the lower right panel is amplified by a factor of three and the spectral windows that are shifted across the spectrum to detect 3LPs are indicated in color. See main text for details.