The title says it all.

One chooses to put the shell in full-screen to maybe inspect a long log, scrolling through it. Continuous unrequested brightness changes which seem introduced by design (their happening is repeatable at the same points when scrolling up and down) are really annoying, and I can't find anything about this behaviour neither in settings/preferences nor googling around ... (a lot about how to set this brightness at system and at application level, but nothing about this behaviour).

How can I turn off this behaviour? I am also interested in understanding the reason behind this "feature".

But I might have seached ineffectively due to my bad english. So if anybody can direct me to the right link, that would be great!

  • Thanks to a phisical colleague (not a internet one, once in a while) I just found something that maybe explains it all, and solves it too. The key fact is that I am working on a notebook and this only happens on the external monitor. I briefly navigated the menu of the latter and easily found an ASCR function in it. I disabled it and the weird effect didappered. I guess that googling for ASCR I will find a more complete explanation. If anybody wants to confirm, I'll post my answer about! – lurix66 Sep 12 '19 at 14:03
  • Yes, that finding is definitely relevant. It's called ASUS Smart Contrast Ratio and it's supposed to turn on a "higher contrast mode" upon certain conditions. It likely works analysing the distribution of luminance and colors of the screen. The bad thing is that you can only turn it on and off, and cannot tune any of its parameters. So it does what it wants and that is annoying. Lucklily I could disable it – lurix66 Sep 12 '19 at 14:13

It turns out that the observed behaviour has actually nothing to do with either Ubuntu or Gnome-terminal, or brightness as well. It is something introduced by the monitor I am using. In fact it doesn't happen on the notebook panel at all (even though the notebook is an Asus, so maybe this feature can be turned on also there).

The matter is the ASCR feature of the Asus Monitor, that seem to think that I am playing some videogame or watching a movie, and therefore I need some contrast boost, then at a later point in the scroll, it thinks I don't need it anymore. Maybe it is the amount of light on the screen, or of coloured pixels... Certainly it isn't anything involving their rate of change, as the switch is permament and brightness would not switch neither back up nor back down if I stop scrolling. Neither the monitor sports any parameters to tune the feature: just an OFF/ON setting. So it seems quite a poorly designed feature.

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