Render transperent shadows in cycles? I am trying to render an animation in cycles without the background. However, every time I have it render, the background still shows up.

I used the compositor to add a background image so I can animate the object around the background. I set the output to RGBA and set the film to transparent. 

Now I want to use it in After effects and I simply want to export/render it without the background and make it transparent.  How do I do that?
I'm not sure what you want, but if I understand correctly, you can make the background image color information remain in the image while still making it completely transparent.

This can be done with the Set alpha node, with an Alpha of 0:



However, in the video you linked to the scene is rendered without any information about the background image at all.

Here is a setup that will do this: