Sunlight simulators that have optical homogenizer units that provide adjustably positionable beams of radiation, each within a selected portion of the spectrum of wave lengths of radiation emitted from a light source, that have uniform output intensity profiles measured across the ends of the optical homogenizer units. These sunlight simulators include either liquid light guides or fiber optic light guides that conduct the beams of radiation, developed from the light source, to the optical homogenizer units. Dosage regulating means control the doses of radiation provided by the optical homogenizer units.