We experimentally investigate the formation of self-confined beams in lithium niobate crystals which are doped in the bulk with erbium. Samples have been grown by the Czochralski method with erbium nominal concentrations varying in the range 0.0–0.7 mol% in the melt. The speeds of beam confinement depend on the applied bias and on the beam intensity, as expected, but on the doping level as well. The erbium incorporation influences both the electro-optic coefficient and the photovoltaic field. A very general dependence of the confined beam waist on the refractive index change was experimentally derived, valid now for every lithium niobate crystal, independent on its growing procedure or doping.