Embodiments of the present invention include structures and methods for enhancing illumination uniformity from solar concentrators. Certain embodiments may use features on a reflective layer to globally correct for deviation in reflective behavior from a desired shape. Local features such as facets on a reflective layer are formed such that the resulting illumination profile represents a superposition of multiple facets. Features may be formed on a back film to correct the reflectance of the back film. In some embodiments, features may be formed on a front film to correct a profile from refraction. In some embodiments the corrections are for line concentrators. Global and local correction techniques may be used together, and may be used on front film or reflective film(s) together or separately. Global and/or local correction may also be used in combination with other approaches, such as secondary optic receiver compensation.