The effect of the hybridization of 4f electrons on La, Ce, and Pr tripositive ions with ligand states or conduction electrons was simulated by reducing the Slater integrals involving the 4f electrons by 10% or 20%, depending on whether the integrand involves one or two 4f electrons, respectively. The dipole-allowed 4d→4f spectra were calculated. Observable effects, changes in line energies, and oscillator strengths, were compared with limited data available for ionic and metallic solids containing these lanthanides, and for Ce vapor. Many of the observed changes in the 4d→4f spectra attributed to hybridization effects are found qualitatively in the calculation.