Hi Richard, Try enabling "Improved Edges" in the GI renderer and also enable "Full Raytracing" at the top of the regular render settings. Interpolation let's Carrara 'guess' where the photons go instead of actually figuring it out. So, interpolation is giving Carrara permission to make mistakes for the sake of improved render times. Full Raytracing will extend the render times but yields better results because it forces Carrara to do complete calculations. You can also try Interpolation in the 80-100 percent range. That will work somtimes but it depends on the scene. Mark