For Gaussian-beam-induced optical limiting based on photoconductive field shielding of electro-optic (EO) birefringence, power-limiting notch widths may be accurately determined by considering the power-limiting threshold for the photorefractive crystal where excess charge accumulates. With sufficient optical intensity the space-charge field completely screens the externally applied electric field, and only a small diffusion field remains. The upper limit of light intensity attenuation is the extinction ratio for the combination of polarizers and EO crystal.