To get total darkness, be sure to click on SCENE in your Instances list (should be the top item listed above all lights and cameras) and then open the Ambient parameter and set it to zero.

For better control of mood light and spill, try SPOT LIGHTS instead of the lights that import from Poser. These are pointable, "cone" spotlights. You can open the "iris" of the spot to get a wider cone of light (in degrees up to 180 degrees). There is also a setting for the "edge" of the cone to be softer (Sorry, Carrara is rendering now or I would get the right words) as if the spotlight were unfocused.... I think this is a percentage of the whole circle

Another control is Falloff which is the distance the light will travel from the source. Set this at 100% and the light will become dimmer over the full distance distance. Set a specific distance (in inches or meters) and the light will end at that distance. The two settings together can be used to (for instance) light a subject without lighting the background.

Hope that helps.

holly