Ya there is also one draw back with using alpha plains. If you need the alpha channel for later work you can't use alpha plains. It don't render properly on the alpha channel. Actually it does render properly and your dirty deed shows up for all to see. The plains show up. What ever is on them don't. ya that's the thing z and a don't work but all is not lost cause you can do it if your missing those channels with Defocus. If your missing those channels it is possible to recreate them with this program.