Stokes I, Q, U, and V spectra of the two Fe I lines at 630 nm recorded by the Hinode spectropolarimeter in a quiet Sun region with integration times of 9.6 s (left), 67.2 s (centre), and 9.8 min (right). The Stokes Q, U, and V panels are saturated at ±10⁻³ I_qs. The linear polarisation signals (Stokes Q and U) stand out more prominently over the slit the longer the integration time, (i.e. as the noise decreases). From Bellot Rubio & Orozco Suárez (2012).