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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.)

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5 Answers

  1. Open Terminal

  2. Enter the following command:

    cat /sys/class/backlight/intel_backlight/brightness
    
  3. Write down the resulting value (12421 in my case)

  4. Divide value by 6 and write it down (2070 in my case)

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

    sudo su -c "echo 2070 >/sys/class/backlight/intel_backlight/brightness"
    
  6. Close Terminal

  7. 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.

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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
    
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 (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. –  pepper_chico Dec 26 '13 at 16:55
    
Why divide by 6? On my machine I could reduce this value much more... –  hoosierEE Feb 11 at 17:46
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Try to override the min brightness manually with

  1. sudo nano /sys/class/backlight/acpi_video0/brightness

  2. Change the value in this file to 0 (clear and type 0 if value is already 0).

  3. Press Ctrl + X to exit.

  4. Press Y and Enter to save the file.

This works for me. You can also try echo 0 > /sys/.../brightness but I get a permission denied message even with sudo.

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

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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
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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
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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 :)

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

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

Works for my intel based MacBook Pro.

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