The most common symptom of not using correct math (gamma correction) in a renderer is that dark areas are too dark. Unfortunately you're using Poser 8 which doesn't have it.

So you will have to manually "correct" the lighting. You will need to do what Dr. Geep said (letting the shadow be more lit than it really is), or you can add more lights.

Or, for a semi-automated solution, you can make the shaders do the correction. I used to use gamma correcting shaders all the time. Making and using the shaders is manual, but once done, the reaction to light will look much more natural automatically as you build different scenes.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)