Birefringence changes induced in LiNbO3:Fe by a light beam have been measured to determine the photovoltaic characteristics such as the saturation value of space charge field, dielectric relaxation time, the probability &fgr; of creating a free electron by an absorbed photon and the mean migration lengthLof the electron. These quantities are determined for different wavelengths covering the region 400–600 nm. The product &fgr;Lthat determines the photorefractive sensitivity of the material increases with decreasing wavelength. This increase is largely due to the increase of &fgr;, the variation of the migration length being relatively small.