Issues with Delta Keyer and Windows -

Hey There,

I'm pretty new to compositing/chroma keying side of video and I'm having an issue on a project.

I have some video that has a green screen covering most of the background (but not all, as I wanted a fairly wide shot of the subject). I'm trying to just have the subject isolated onto a different background (in this case an underwater stock footage shot).

I have tried using a window in the colour page (to remove the non-green screen background), and then a delta keyer in the fusion page (to remove the green screen) but this means that everything outside of the window becomes black, not transparent. I have attached a photo showing what I mean.

What would be the correct workflow for what I'm trying to achieve?

Instead of using the window in the colo(u)r page, use a polygon mask in the Fusion page and pipe that into the Garbage Matte Input of the Delta Keyer. (there's a good chance you'll have to invert it in the polyline settings) and you should be good to go.