Vignette is distorted and not symmetrical Situation: I am setting up a Vignette effect for my scene. Like what I do normally, I have a lens distortion node, math node (set to 'greater than'), blur node, and a mix node (set to multiply).

Problem: However, for this scene, the vignette effect seem to have a weird shape and it's not symmetrical either. Below is the result. How do I fix this? Thanks.
Here is my blend file
That weird shape looks a hell of a lot like a distorted mountain to me. You shouldn't plug your source image into the Lens Distorsion. You could instead take a Distort-->Scale node, in Render Size mode, so that you have a totally white image.