How to mask one image and layer it over another? I'm trying to add parts of a blurred picture over the crisp version of the picture. I want to create a blurred corners effect.

This is the original picture:


This is the vignette I want to overlay:


I tried to combine the two using Alpha Over, but the blurred version doesn't show:


I tried using Mix with a variety of modes (Add, Overlay, Multiply), but I don't get the right results. Multiply is closest but too dark:


I tried adding a Set Alpha node in various places, but if that's the solution, I don't know where to put it.

How can I layer the vignetted image over the original image?
Use the blurred ellipse mask as alpha with the set alpha node.

I guess you wanted the white to be none blurred, hence the following Invert node with Alpha checked.