Comparison of the first eigenvectors resulting from the PCA analysis for the observed and theoretical Stokes I profiles (top row), V profiles (middle row), and linear polarisation profiles (bottom row). The black curves correspond to observations, the blue curves to the theoretical profiles that are not degraded with a spatial PSF, and the red and green curves represent the theoretical profiles degraded with PSF_{r0=10 cm} and PSF_{r0=5 cm}, respectively.