Hello there, I am not able to reproduce the aforementioned issue on Youtube using the latest Firefox release. Any gamma value above 0 produces the expected filtering. Is there a particular page on Youtube that is having issues, or all videos, even on other websites? Are other filters enabled at the same time? Do you have any other video related add-ons installed? What operating system are you using? Feel free to post an issue on GitHub (https://github.com/PyvesB/night-video-tuner/issues) to continue the discussion. ;-)