Quote - i noticed that if you use a backlight that it is not very bright. its actually pretty dark.

You mean just a single light from behind? You turned off or did not use IBL? Yes its dark - in fact its pitch black, because Poser does not do global illumination. So there is ZERO light reaching the front of the spheres.

If you were to do this test in a renderer that had global illumination, the front of these would be lit quite a bit by the floor.

This is why I always use at least a low-level IBL, to simulate the ambience produced by diffuse inter-reflections among the items in the scene.

even with an IBL IMO it is dark. at least in my renders. if i have a white light behind my object then there should be a white edge. right?