Field of view at three different wavelength positions −0.945, −0.28, and 0.0 Å from the line center λ₀ = 8542.1 Å. Lower panels: average line profile and vertical dashed line at the wavelength used to generate the FOV of the upper panel. We see how the spectral line has information from the photosphere (left column) to the chromosphere (right column) where the filament is observed.