On my new Dell XPS 13 9370, it seems that the display backlight brightness is adjusted based on the brightness of whatever's on the screen.

For example, say I have Sublime Text open with a dark theme, and I click on the file menu. The menu dropdown has a light background, and this is enough to darken the entire screen. Moving the selection over to the "Selection" menu causes the screen to lighten back up again, because this menu is apparently small enough for it not to count.

You can see the effect here, as I switch between a larger and smaller menu:

Unwanted brightness change

I find this feature unpleasantly jarring as I navigate through menus and similar. Is it possible to turn it off?

In case it is relevant, my system specs are as follows:

  • Dell XPS 13 (9370)
  • Debian Linux (sid)
  • Cinnamon DE
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    Why would Dell ever think this is a good idea? – Ian Kemp Sep 3 '18 at 6:01
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    @IanKemp It looks like a terrible implementation of something that would be useful in some circumstances. For example, there's a TV show I'm watching at the moment where the banner before and after the ad breaks is an almost entirely white screen that's eye-burningly bright if I'm watching in a darkened room. If my laptop fixed that for me, I'd be delighted. – David Richerby Sep 3 '18 at 13:23
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    @Mala: please edit the title: widow should be window, but users reject my edit to fix this. – Patrick Hofman Sep 3 '18 at 13:36
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    @PatrickHofman That's bizarre. I submitted the same edit without knowing about yours and people were sensible and accepted it. – David Richerby Sep 3 '18 at 16:29
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    @PatrickHofman Reviewers are often silly (I wanted to use a stronger word). IMO every one of them in this case should be banned from reviewing but that's not a battle we'll ever win – Lightness Races in Orbit Sep 3 '18 at 18:03

According to Dell_Guy on the Dell.com community forums:

You can fix this by disabling Dynamic Brightness Control under the BIOS settings.

Original Quote from Link:

You can go into BIOS settings (hit F2 as you are restarting your computer) - and DISABLE Dynamic Brightness Control in the display options. I don't know if you need to update the laptop to the LATEST bios to have this option (I did the update).

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    Just commented the exact same thing :) – BobtheMagicMoose Sep 3 '18 at 2:47
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    Wonderful! Thank you very much. I had always figured "Dynamic Brightness" referred to adjusting brightness with regard to ambient light, but reading closer in threads linked to from the one you refer to, I see "This is related to the displays Dynamic Backlight Control (DBC) technology. This feature will change the brightness of the display according to the content shown on the screen." – Mala Sep 3 '18 at 3:19
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    Oh, they finally made it a BIOS setting? I remember a long Github thread about this misfeature having been permanently embedded in the LCD panel's firmware, and indeed in my Inspiron 5547 it only went away after the panel broke and got replaced. – user1686 Sep 3 '18 at 7:09
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    Wow, this is absolutely crazy. Who would even think of putting this into a laptop? – pipe Sep 3 '18 at 14:53
  • What is the point of this feature? It saves battery life? – becko Oct 27 '19 at 12:07

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