Good points maxxxmodelz. Don't use both at the same time. One thing that helps to make the decision whether to use AO on a light or on a material surface is knowing that doing it scene wide on a light will require the raytracing engine to compute the effect only once. If you put it on a surface material, Poser will need to compute it for each material separately. That might take much longer, depending on how many surfaces you use the effect. While it looks best on the IBL, any light type will allow you to activate the global AO. Uli