Yes a mask would achieve this easily.
You need to have one group layer (or bone layer) for the masking. Inside that group you need 3 additional layers. Here is how it should be setup:
Group (or bone) layer - masking property set to
Hide All
--->
1. scene layer (or group layer) - Masking property -
Mask this layer
--->
2. Spot light layer - Masking -
Add to Mask but keep invisible This shape should be the same color as the back ground layer. It can be just a simple filled circle shape.
--->
3. Black background - Masking -
do not mask This could be just a filled box shape that covers the whole scene area.
Turn on masking in the preview and you should now see a "hole" through the black revealing the scene. You can add more shapes to the mask layer if you like creating as many light sources as needed.
What is happening is the mask is creating a "white" hole (Add to mask) in the already completely "black" mask (Hide All). The black of the mask has NOTHING to do with the black background layer or any colors. White and black are just terms for alpha channels involved in masking. Just thought I would mention that. The mask and background layers could be any color.
In fact you don't need that last layer at all. You could set the back ground color of the project file to black (or any color) and it would still work.
The masking shape on the "spot light" layer MUST be the same fill color as the back ground color. The reason for this is that some of that "fill" color in the mask will be seen ever so slightly in the fuzzy edge.... if you don't use the soft edge effect on the spot light layer then the color doesn't matter.
If you need more info on masking see this thread in Tips and Techniques:
viewtopic.php?t=9669
-vern
I'm doing a scene where it is pitch black everywhere except for specific lit areas or a flashlight moving around. You can only see what's near or around the light source. I was wondering how that can be achieved? Would using a mask work? 