A model to describe fanning effects in photorefractive crystals is presented. The intensity distribution of the fanning beam for one incident beam and two incident beams in 45°‐cut BaTiO3crystals has been studied theoretically and experimentally, with good agreement. The theoretical results suggest that, when there is a fanning effect, only at intermediate effective interaction lengths does the signal beam have a high gain in two‐wave mixing. The transient behavior of the fanning beam in a 45°‐cut BaTiO3crystal has also been studied theoretically and experimentally.