Is there a way to output two videos from rendering - one with compositing and one without? So I have a scene with a fluid simulation and I want to know if the result is better with or without the vector blur node.

Is there a way to render a video where blender first renders the image and exports it to a file and then adds the compositing nodes and exports the image to a different file?

This way you will get two video's at the end, one with compositing and one without.

This would save a lot of render time because you only have to render it once.
Yes you can do that.
Use a file output node in the compositor. 



How to output multiple images from Blender&#39;s compositor with Python?