Hi @Mugen87, took me a bit, but finally I managed to reproduce it in a fiddle.
I put a 2s timeout to switch from the default renderer to the composer.
By default (with the OutputPass added), you can see the scene turning “brighter”.
If you comment it out (line 594) and rerun it, it will turn darker.
But it will never reproduce the original result.
Forgive the bloated setup in the beginning, I needed to build something similar to what I have.
And really appreciate you looking into it, thank you!