I have fixed this bug! Adding this parameter to boot offers the correct behavior of screen brightness. It seems to be an upstream issue and not related to gnome power manager.
acpi_backlight=vendor -- Lucid - Screen Will Not Dim Automatically https://bugs.launchpad.net/bugs/543995 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs