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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
bertieb
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Mala
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    Check if there's a new UEFI available and update. Newer versions should have a switch to enable/disable DBC (Dynamic Backlight Control) but not all models benefited from this new firmware. –  Sep 03 '18 at 02:48
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    Well, there is an update https://www.dell.com/support/home/uk/en/ukbsdt1/drivers/driversdetails?driverId=60JF1 but doesn't mention DBC explicitly. Perhaps your version already has it? –  Sep 03 '18 at 02:51
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    Why would Dell ever think this is a good idea? – Ian Kemp Sep 03 '18 at 06:01
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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 03 '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](https://superuser.com/review/suggested-edits/786582). – Patrick Hofman Sep 03 '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 03 '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 03 '18 at 18:03
  • @LightnessRacesinOrbit just for information: [When is editing encouraged or discouraged](https://superuser.com/help/privileges/edit) excerpt: **Tiny, trivial edits are discouraged** - try to make the post significantly better when you edit, correcting all problems that you observe. – Nordlys Jeger Sep 04 '18 at 08:42
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    @NordlysJeger That advice is controversial and "widow"/"window" in the title is obviously a candidate for a quick fix. If you do a search on Meta Stack Exchange you'll find long discussions on the topic, including my views. Welcome to SE! – Lightness Races in Orbit Sep 04 '18 at 10:15

1 Answers1

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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).

Michael Frank
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    Just commented the exact same thing :) – BobtheMagicMoose Sep 03 '18 at 02:47
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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 03 '18 at 03:19
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    Oh, they _finally_ made it a BIOS setting? I remember [a long Github thread](https://github.com/advancingu/XPS13Linux/issues/2) 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. – u1686_grawity Sep 03 '18 at 07:09
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    Wow, this is absolutely crazy. Who would even _think_ of putting this into a _laptop_? – pipe Sep 03 '18 at 14:53
  • What is the point of this feature? It saves battery life? – a06e Oct 27 '19 at 12:07