Transparent background
 

I need to render a frame but I need the background to be transparent so it can be used on a matte painting. I really should know how to do this by now so if anyone could let me know it would be much appreciated.

Many thanks,

Leon

Make sure you render the object with an alpha channel and save the render to a format that supports alpha's ie tiff, targa ect so you can use the alpha to mask out or delete the background in your 2D or compositing package later.