To simplify the problem, I’ve set up this example scene:
I’ve rendered a simple sphere with an emission shader and a transparent background. In the compositor I blured that image and put it ontop the same unblured image using the alpha over node. (see screenshots) I then exported an image right after the blur (nr. 1) and at the end (nr. 2).
For some reason the alpha over node seems to mess up the Alpha channel.
The problem is not noticable in the compositor itself, but when exporting it as a 32 bit exr and importing it into Blender or photoshop, you can cleary see the difference. Even when you look directly at the alpha channel.
What could be a fix for that?
I’ve noticed this problem in a much more complicated project and narrowd it down to the alpha node.
