Left: 3D Fe abundances from Fe i and Fe ii lines, as a function of equivalent width and lower excitation potential. Right: line-by-line differences between abundances obtained with the 3D and ⟨ 3D ⟩ models, and between those obtained with the 3D and HM models. Filled symbols and solid trendlines indicate neutral lines, open symbols and dotted lines indicate singly-ionised lines.