I've decided that the Bryce "camera" is a low contrast, high brightness machine. Try rendering a scene and then look at the levels in Photoshop. The levels are usually skewed and they're difficult to "correct." Never push the "Auto Levels" button!
I have a vague recollection of reading about a way to adjust the camera before you render. Not sure it's worth it and they may have corrected that in the latest version.