Left: response functions of intensity to temperature at the five chosen spatial positions (see Fig. 2). The response functions are normalized to unity but are displayed here in the range 0–0.5 for improved contrast. The LTE intensity profiles in red color are overplotted on these 2D maps. Right: comparison between LTE and NLTE intensities at the five spatial positions marked in Fig. 2. δI and δE are the relative differences in intensity and equivalent width defined in Eqs. (3). The subscripts 1 and 2 refer to the 6301 Å and 6302 Å lines, respectively. At pos. 5, δI₂ is not indicated as the line profiles are Zeeman split.