Blender 2.62 - Exporting shadow passes

I am a blender newbie. I am trying to render individual shadows, without the floor or the object. I am using either Luxrender or Blender render. I can’t find a way to export just the shadow passes. Actually, I can’t even find a way to show just the shadows without the objects. In short, what are the techniques in blender to export passes for compositing?
Many thanks

With Blender materials for the internal renderer (not Cycles), in the Materials panels check Shadow -> Shadows Only. This will render the material using only its alpha values, ie any part of the object not receiving a shadow will be transparent.

Another way is to set up a renderlayer containing your shadow-receiving object and turn on the Shadow pass for that renderlayer. Then you can use the Shadow output to render your mask.

Thank you. Will try that. Is the same possible for diff, spec, normal, fresnel etc in blender render? I notice in cycles the displacement tab list much of the passes I am interested in. Do you think this has a correspondence at output? I am looking for a manual but can’t one that i understand.