Decrease Backlight Below Minimum

Question

I have this laptop that doesn't handle the backlight very well.

In /etc/default/grub, I have added a acpi_backlight=vendor function to get it to work at all. Which is cool, and the backlight now actually works, but the minimum backlight setting is still pretty high.

Is there any way to decrease the backlight below minimum? I don't mind having to type in the terminal to do that, as I won't need to do it often (just at night etc.)

score 47 · Answer 1 · edited Nov 13 '19 at 03:18

47

Open Terminal (Ctrl+Alt+T).

Enter the following command:

cat /sys/class/backlight/intel_backlight/brightness

Write down the resulting value (12421 in my case).
Divide value by 6 and write it down (2070 in my case).

Enter the following in the terminal, replacing 2070 with your value:

sudo su -c "echo 2070 >/sys/class/backlight/intel_backlight/brightness"

Close Terminal.
For future usage of the last command, open Terminal, press Ctrl and R together, start typing brightness. When the last command appears, just press Enter.

It works for me on a Samsung NC110 with Ubuntu 12.04.

edited Nov 13 '19 at 03:18

Eliah Kagan

117,780

answered Aug 13 '12 at 12:23

mIRLek

499

Works for me in Ubuntu 12.04 on a Macbook Air (integrated Graphics only). However, pressing any brightness level button seems to reset this setting, i.e. pressing "brighter" does not increment from the brightness setting applied in the terminal, but from the "usual" minimum brightness that you achieve using the keyboard. Therefore increasing the brightness after applying this command results in a huge brightness increase. – king_julien Jul 28 '13 at 21:27
2

Aaaaaaaaaaaaaaaaaaargh. This setting resets itself automatically every few minutes. So you got to reapply it over and over. In it's current format this is not a practical solution :( Running it as a script periodically seems overkill though. I hope there's a better way... – king_julien Jul 28 '13 at 22:04
@king_julien, check my answer (http://askubuntu.com/a/394400), at the provided link I tell about some settings that may avoid resets. I'm not suffering any reset of this setting at my macbook pro. I suspect the reset has to do with the boot parameters. Since I've changed them, I'm not suffering a "reset" after unlocking the machine. – oblitum Dec 26 '13 at 16:55
5

Why divide by 6? On my machine I could reduce this value much more... – Alex Shroyer Feb 11 '14 at 17:46
2

sudo su -c "echo 2070 >/sys/class/backlight/intel_backlight/brightness" is the key, the number can go as down as 0. I use 80 on pitch black rooms. On 14.04. – quimnuss Nov 25 '15 at 12:14
2

When I try values between 0 and 1 I get an error: echo: write error: Invalid argument Is there a solution for that? – TenLeftFingers Jul 20 '16 at 00:11
This used to work in Ubuntu 16.04, but doesn't anymore in Ubuntu 16.10 :-( – starbeamrainbowlabs Mar 04 '17 at 18:05
Wow I had no idea my screen brightness had this much granularity. I don't know why you're dividing by 6 here, but on my laptop it seems to be that any number works. The normal lowest brightness was 376, but I found 20 to be very nice in a dark room at night. – nog642 Aug 14 '23 at 17:52

jeshurun · Answer 2 · 2017-11-12T04:34:55.223

39

None of the answers here worked for me (on a Dell Precision 5510). The output from cat /sys/class/backlight/intel_backlight/brightness for me was 1 and setting it any lower completely turned the screen off.

I finally found a solution from the answer here:

xrandr --output eDP1 --brightness .3

I was also able to get this to work on my external monitor (attached via a display port dock), and reduce it below the minimum brightness allowed by the hardware controls on the monitor:

xrandr --output DP1-1 --brightness .6

Note that your display might not be eDP1 (or DP1-1), but you can list all available displays by hitting tab twice after --output, or from xrandr -q which shows which ones are currently connected. Tweak the value for brightness, i.e., .4, .5, etc until you find a level that works for you.

edited Nov 12 '17 at 04:34

answered Apr 27 '17 at 05:08

jeshurun

848

How do you make this change permanent? – Prakhar Agrawal Mar 27 '18 at 13:41
1

is there a way to get nightlight with this as well? when i use it, nightlight goes off and i get bluer tints – jeremy_rutman Apr 29 '21 at 22:19
OMG OMG first time in my life I faced the power of Linux hack like this, and I use Linux for many years, xrandr --output eDP-1 --brightness .6 this did the trick from me BTW .3 were like someone turned off the like, now I have beautiful semi Black/White screen to watch . – Salem F Sep 26 '21 at 22:33

score 4 · Answer 3 · edited Mar 12 '15 at 01:36

4

Try to override the min brightness manually with

sudo nano /sys/class/backlight/acpi_video0/brightness
Change the value in this file to 0 (clear and type 0 if value is already 0).
Press Ctrl + X to exit.
Press Y and Enter to save the file.

This works for me. You can also try sudo sh -c 'echo 0 > /sys/class/backlight/acpi_video0/brightness'

I am still looking for a more robust approach. Any help is appreciated.

edited Mar 12 '15 at 01:36

David Foerster

36,264
56
94
147

answered Feb 19 '12 at 08:07

Arian

41

1

It doesn't seem to recognise the folder/file. I'm on Ubuntu 11.10, if that makes any sense to you. Thanks for caring to answer, though. – Ruben Bakker Feb 20 '12 at 20:35
2

I tried doing suggested. However the brightness still remains the same. In my case it was already 0 . Although I cleared and reentered as suggested. – bubble Nov 22 '12 at 17:42
This file does not exists in 12.04. – king_julien Jul 28 '13 at 21:21
Different GPUs / hardware have it in different places – Suici Doga Jul 07 '16 at 06:34

score 3 · Answer 4 · answered Nov 13 '22 at 23:22

3

The Gnome Shell extension Alpha Tint has solved the issue for me in Ubuntu 22.04.1 LTS (Wayland).

answered Nov 13 '22 at 23:22

FelipeE

31

This is the only one which worked for me. Thanks :) – dark32 Nov 19 '22 at 09:22

score 2 · Answer 5 · edited Jan 16 '18 at 12:34

I'm not using Ubuntu but Debian, but sometimes (second screen plugin, gnome restart) the brightness drops to zero. So I've created an inotify enabled application (it consumes zero cputime while there is no change in brightness) and when there is the change and it is changed to zero (or lower some predefined level, which you can specify) it sets the brightness to some default level, which you can also specify.

Please find it at my github page: https://github.com/nuccy/zero_brightness_fixer

score 1 · Answer 6 · answered Nov 24 '22 at 01:29

1

The Gnome Shell Extension Soft-brightness did the trick for me.

answered Nov 24 '22 at 01:29

Dima

141

yes it did the trick for me too! – ProPlayerMaxUltra Jul 27 '23 at 05:47

score 1 · Answer 7 · answered Apr 19 '13 at 11:18

1

Install xbacklight by typing the following in the terminal

sudo apt-get install xbacklight

then:

xbacklight -percentage

replace the word "percentage" with the number of your choice to decrease the backlight from 1 to 99. In contrast, you can also do:

xbacklight +percentage

to increase the brightness by replacing the word "percentage" with a number between 1 and 100. For more information, run the following in the terminal:

xbacklight -help

I know that this is probably too late, but I hope it helps :)

answered Apr 19 '13 at 11:18

Fikra

19

4

This does not decrease the backlight below minimum. When I'm already an the minium and just step -1, the display shuts off. – king_julien Jul 28 '13 at 21:18
Didn't do anything.no matter what setting I used. – Jeff Luyet May 19 '23 at 18:28

Jeff Luyet · Answer 8 · 2023-05-19T18:24:28.433

0

This should work for a lot of GPUs:

echo 0 > /sys/class/backlight/$(ls /sys/class/backlight/)/brightness

For Ryzen APU's its:

echo 0 > /sys/class/backlight/amdgpu_bl0/brightness

edited May 19 '23 at 18:24

answered May 19 '23 at 18:12

Jeff Luyet

183

score 0 · Answer 9 · answered Sep 06 '13 at 04:56

0

This app works for me for decreasing brightness well beyond the usual https://github.com/lordamit/Brightness

answered Sep 06 '13 at 04:56

user13107

778

Looks interesting. Care to share your binary? – TenLeftFingers Dec 13 '15 at 23:52
@TenLeftFingers sorry, dont have that machine now. – user13107 Dec 14 '15 at 09:58

oblitum · Answer 10 · 2019-11-21T15:23:46.523

0

This tool is a slider utility to set /sys/class/backlight/intel_backlight/brightness:

https://gitlab.com/oblitum/backlight

Works for my intel based MacBook Pro.

edited Nov 21 '19 at 15:23

answered Dec 22 '13 at 17:40

oblitum

1,687
2
16
27

Decrease Backlight Below Minimum

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