I'm a Poser (6) newbie, but do have some serious 3D (LIghtwave, etc..) experience. 
I can't fathom the apparent oversight of not having -in Poser 6-  a global ambient light setting...perhaps there is a python script or something I'm not finding? 

What am I trying to do? Well, for example, increasing the global ambient light will lighten every thing uniformly,  and decrease shadows uniformly.  I estimate having this feature would cut my time on lighting by ...a whole bunch. That's a technical term that I rarely use :)