Volumetric fog messing up alpha channel

[Gianni333]

It seems that Volumetric Fog is creating some kind of white fringing when I try to exchange the sky in post.

The second image attached is rendered with volumetric fog, saved as a png and another sky added as a background in post. The first
image shows the exact same process but rendered without volumetric fog. There is no white fringing whatsoever.

Is there a way to fix that?

[maru]

For compositing like this, you should render the objects against a pure black background. Are you doing this? If you render against the fog, you will most likely end up with the white fringes.

[Gianni333]

Sorry I missed your reply, but I ended up doing what exactly you suggested. That solved the issue. Anyway thanks a lot for your answer :)