Fig. 7a and b. Spatially averaged longitudinal field, derived with the centre-of-gravity method, normalized to its value at disc centre, vs. µ. Plotted are the results for unbroadened profiles from models B, D, E, and PLA. Macrotrubulence-broadened profiles give practically identical results. a  Fe I 5250.2 Å, b  Fe I 5247.1 Å.