The spectral and geometric trends of Ln(trensal) complexes (H(3)trensal = 2,2',2"-tris(salicylideneimino)triethylamine) along the lanthanide series are analyzed. Low-temperature polarized absorption and luminescence spectra are reported for nine of the complexes with transitions suitable for analysis. Both the angular and radial geometry variations as a function of the lanthanide ion are quantified. The structural parameters are related to the trend in the ligand field found from an analysis of the f-f transitions. The ligand-field analysis is fitted globally across the whole series accounting for the contraction of the f orbitals as a function of atomic number. This study establishes the utility of describing the ligand field of f electrons within the one-electron operator approach of the angular overlap model.