Example of determining σ_w and p_w by removing the π-component in the intensity profile (Stokes I; top left panel) in a pixel in which the magnetic field is aligned with the observer line of sight. Black lines represent the observed Stokes profiles I^obs. Red lines show the wide-angle contribution (i.e., scattered light) from the surrounding penumbra and quiet Sun, . Blue lines represent the observed Stokes profiles after removing 20% of the wide-angle contribution. See text for details.