This is actually 2 seperate questions.

First, I would like to know if it is possible to render shadows out without a floor. I know that sounds odd... but I want to do this for a composition. If you render out a scene, you can save it as a .psd file, which will keep tranparency intact. What I would like to do, is have only the object and its shadow in the render, so that "all I have to do" is setup the appropriate perspective, render, then drag and drop the .psd into my background and the shadows are already there. Essentially I want a "render" of my object and its shadow. Is this even possible? Do you create a floor and render something similar to layers so that you can just turn off the floor?

Second, I want to create a studio type scene for an object. I want it to be inside what is pretty much a big white box. I want to test shadows and perspective and I figure this is the best way, then I can maybe import a background image to help with camera angles and such. In a studio, you usually have more than one light, but you want to keep only one (distinct) shadow (to represent only 1 light source) and you don't want the walls of the white box to cast shadows. So, what would be the best lights to use (can you turn off cast shadows on specific lights?) and how do I turn off the wall shadows? Keep in mind I just want this to be like a commercial with a stool in the center of a white room, pretty much equally lit.

Thanks.

Edit: Also, how come depth map shadow resolution doesn't match the image resolution. If you use 1024X768 as your image resolution and 1024 as your DMS resolution, the shadows look terrible.