Photo-induced light scattering in iron doped lithium niobate crystals is investi- gated at different wavelengths in the near ultraviolet spectral range. Holographic scattering is applied to probe the photovoltaic and diffusion contributions to the photorefractive effect. We found that the magnitude of the photovoltaic effect is decreasing from 364 nm to 334 nm, and diffusion becomes the dominant charge transport mechanism for photorefraction.