3D LTE versus 1D LTE abundance corrections as functions of 3D LTE reduced equivalent widths, W_reduced = W∕λ, for different Fe II lines. The arrows show how the results change by increasing the metallicity [Fe/H] (noting that the iron abundance is always kept consistent with the atmospheric chemical composition as labelled by [Fe/H]; Sect. 2.3). Thus the curves are for fixed effective temperatures and surface gravities roughly corresponding to the nodes of the 3D STAGGER grid in Fig. 1. The 1D microturbulence was fixed to ξ_mic = 1.0 km s⁻¹. Also plotted are approximate abundance corrections for some reference dwarfs, adopting the stellar parameters listed in Table 1 of Amarsi et al. (2018b). The effective temperature of Procyon (T_eff ≈ 6556 K) lies slightly outside of the grid of 3D models and the abundance corrections are extrapolated here.