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My laptop's screen is far too bright at night, even if I set it to minimum brightness. I know that it is capable of being dimmer, because Windows will dim it further if I leave it idle. However, I can't figure out how to dim it lower to minimum on Ubuntu. Is there a way?

I've looked at this question, but it's talking about Windows.

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If the back-light is set to the minimum, then that is all you can do with it. Try adjusting the brightness, contrast, and gamma of the video-card with something like xgamma or other program. – Synetech Jan 3 '14 at 5:09

Here is a link specifically addressing setting screen brightness below the minimum:

Decrease Backlight Below Minimum – Ask Ubuntu

  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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That gives better control within the standard range. I want to go outside the standard range. – cpast Mar 4 '13 at 6:05
    
For me, this dimmed the screen well past the minimum. :) (Lenovo Y50) – Chris Cooper Dec 19 '14 at 4:31
    
Also worked great with 14.04 on acer E15. +1 – Publi Design Mar 6 '15 at 5:01
    
I get cat: /sys/class/backlight/intel_backlight/brightness: No such file or directory from the first command. Is it because I have a discrete video card (GTX460M) in my laptop? (I'm on Ubuntu 14.04 LTS) – Borgleader Jul 8 '15 at 1:13
    
@Borgleader Yeah, just look in /sys/class/backlight for the folder corresponding to your video card. – Azmisov Sep 19 '15 at 7:21

you can also use "xgamma -gamma 0.5" command to decrease the intensity of RGB colors. See xgamma usage by using command "man xgamma". For my intel display the gamma brightness varies from 0 to 10(including decimal values).

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