Scatterplots of continuum contrast vs. apparent longitudinal field strength B_app,los for the boxes shown in Fig. 1, pores excluded. Red crosses: average values of the continuum contrast inside B_app,los-bins of 50 G width. The red error bars are the standard deviations inside each bin. Solid red curves are third-order polynomial fits of the average values in the range 200 G  < B_app,los < 1000 G. Blue arrows: indicate the peaks of the trend of the contrast vs. B_app,los. The vertical solid blue lines at B_app,los = 100 G separate the “weakly magnetized areas” used as contrast and velocity reference and the “magnetic patches”. The dashed blue lines at B_app,los = 500 G is the upper limit below which pixels can be considered as not belonging to magnetic features.