As in Fig. 3 but showing only the results of PF on the binned curve over |B_LOS|/μ (yellow curve) by varying the |B_LOS|/μ threshold, i.e. the magnetogram noise cut-off (dotted coloured curves). The threshold is 1 G for the black curve and rises to 50 G for the red curve. The curve corresponding to the 20 G threshold adopted in this study is shown with the light-blue solid curve. The thick yellow curve shows 5000-point running mean over |B_LOS|/μ. The vertical grey dashed line denotes the 20 G threshold in |B_LOS|/μ.