Line profiles, response functions, and magnetic fields in three representative atmosphere models. Top row: Intensity of the Ca II H line before (blue) and after (orange) being convolved with a spectral PSF of 130 mÅ. Second row: Circular polarisation of the Ca II H line before (blue) and after (orange) being convolved with a spectral PSF of 130 mÅ. Third row: Image of the response functions of Stokes V in the Ca II H line to variations of B_LoS, as function of wavelength expressed as Doppler shift and column mass ξ. The three dashed curves correspond to the location on the log ξ vs Δλ space of the maxima of the response functions for the Ca II H (blue), K (orange), and 854.2 nm (cyan) lines. Bottom row: Stratification of B_LoS obtained from inverting the synthesized Ca II H and K spectra compared to the input atmospheric model. Vertical lines on the bottom row represent estimations of the uncertainty of the B_LoS at chosen depth points.