Have you tried using "Soft Shadows" in the lighting lab ?(Can be done on "Normal" render setting) You can also use "Shadow Ambience" to adjust the intensity of the shadow colors. Of course this will dramatically increase render times. You could also use the materials lab to adjust the texture "ambience" color to a lighter color than black, say a semi-dark charcol gray. Definitely adjust the shadows using the Skylab as suggested by Aldaron. Take them to a very light gray at around 50.

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