I made myself a frame out of PVC pipe and hung a fine netting over it which I then ran down into a plastic trough. The netting is hung loosely enough that when the brass strikes it it puffs out and absorbs the shock so that the brass then just drops down into the trough. I get about 90% of the brass into the trough with the other 10% of it within easy picking up range of it. Since I made this thing I haven't lost any brass. I also lay a small tarp down under the whole rig to make the end clean up easy. I use one of those little brooms and the things that ushers in theaters use, the bucket on a swivel on a stick, to pick up the errant brass that lands near the trough.
This has allowed me to pick up all of my brass without bending over, or at least with a minimum of it.
I tried to patent my "Brass Catching Drape" but it seems that it wasn't something I could patent as it was already in common usage, like in tennis courts and batting cages and driving ranges. When I said my use was unique, that seemed not to hold water. Oh well, back to the drawing board.
(I have not ever seen this in use in any of these places though and there it is, already a "Common Use" product and therefore not able to be patented) bah! ;D