Alpha on a Merge?

How do I apply an alpha to a merge? I've merged together a bunch of exr outputs from a 3d program and would like to apply the alpha output to that and then apply the result to an image plane. I can't seem to figure out how to apply the alpha though.

Probably several ways of going about it. I'm not exactly sure of what your setup is, but I think one way would be to use the channel boolean tool after your merge. Pipe your merge in the BG and the alpha in the FG, and copy the alpha or luminance in the alpha channel. Give that a try and see if that's what you're looking to do.

Perfect! Thanks!