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Is there a way to adjust lighting step ? I have Lenovo L520, and Fn + Light Up or Down adjusts by 20%, how can I adjust the step to 10% ? it will help me fine tune lighting at my dark room.

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@ఆగస్ట్ It's not a dupe of that one but these two are exact dupes, yet this one here is the oldest. The other two should be closed instead. – Tom Brossman Oct 8 '12 at 18:22
yup! you are right amigo . i will do the remaining job then :D – Raja Oct 8 '12 at 18:25
Given that most firmwares/OSs default to increments of 10%, your issue sounds like you just needed to apply the well-documented method of adding acpi_backlight=vendor to your GRUB configuration. – underscore_d Oct 18 '15 at 23:19

11 Answers 11

Install xbacklight by opening a terminal with Ctrl+Alt+T shortcut and type this:

sudo apt-get install xbacklight

then after installation, type these commands in terminal:

xbacklight = 10
xbacklight = 20
xbacklight = 5

this may help.

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This method worked perfect for me! Other way is: xbacklight -dec 1, or xbacklight -inc 1 (to increase or decrease 1%) – lepe Dec 13 '12 at 13:06
On a Asus n55s xbacklight accepts any value (even with decimal places), but actual values (as visible by try and see, and as returned by xbacklight without argument) are rounded down to the nearest 10%. – Stéphane Gourichon Jun 3 '14 at 20:09
It should be noted the man page recommends -set instead of =. More importantly, anyone mapping keys to this should really add -time 0 -steps 1 - because otherwise, xbacklight applies backlight fading by default, which seems to really wind up your (at least my) CPU when 'scrolling' brightness by holding down the assigned hotkey. I'm talking all cores rising from 45 to 60 degrees, over just a few seconds - best avoided. To be fair, I'm using 1% increments - where fading is even more pointless than normal - but still, don't tax your CPU if you don't have to. – underscore_d Oct 18 '15 at 23:06

There is a file in Ubuntu which stores numerical integer value of brightness. you will find 3 files in the directory /sys/class/backlight/<VGA>directory replace directory with intel_backlight for intel cards.

You will find the max brightness value in max_brightness file and according to that value set the brightness in brightness file.

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This was shows if your hardware is capable for fine granularity or not. – V-Mark Jan 14 at 9:15

As Colin Ian King said, the levels of brightness are hardware related.

Some laptop screens have 8 levels of brightness and new ones have 16 levels.

On Windows OSes you can change the levels with 1% steps, but they will be rounded to the nearest hardware level. It depends on the screen type.

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The brightness levels are generally under ACPI control with the levels defined in firmware. For example the ACPI control method _BCL "Query List of Brightness Control Levels Supported" informs the kernel how many brightness levels are supported. You can't realistically change this.

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You can install xcalib and then type the command:

xcalib -co 50 -a

Use xcalib -h for help regarding it's options.

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Brightness cannot controlled with large precision. I'm afraid that you're stuck with those brightness levels. To be sure, try controlling the brightness using these terminal commands.

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If I go to System Settings, I find an icon labeled 'Screen' If I click on that icon I get a scroll bar that can set the brightness in small percents, How can I get this screen icon to the top bar ( besides clock, or battery indicator ) ? – Samir Sabri Feb 11 '12 at 9:13
What about I haven't tried it since I don't use Unity/GNOME. – Lekensteyn Feb 11 '12 at 10:17
Oh, sorry, thanks but, how to install it ? – Samir Sabri Feb 11 '12 at 19:25
Have a look at – Lekensteyn Feb 11 '12 at 21:08
It definetely can be controlled in smallest steps in many cases. Please have a look at – vines Oct 25 '12 at 0:30

You could try setting it manually. First you have to get the PCI-ID of the VGA device:


Then try this (in my case the PCI-Device is 00:02.0)

sudo setpci -s 00:02.0 f4.b=FF

The 2 letters at the end of the Line set the new brightness ranging from 00-FF (0-255)

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If you are using Nvidia Graphic can easily use my new method of brightness changing,and edit values in Code.. theres two files and two options within each one.

find these two lines:

if ( $value > 0.0) { $value = $value - 0.30 };  
if ( $value2 > 1.1) { $value2 = $value2 - 0.08 }; 

change values of ($value > 0.0) & ( $value2 > 1.1) and see whats happens!

meanwhile if you dont want to change values and wish to use my method originally you can change brightness in a wide range and 5 steps. wish you like it

link of method:

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Uh... isn't this just mangling the bitmap before it's sent to the screen, rather than actually changing the screen's brightness? – underscore_d Oct 18 '15 at 23:14

In my case (Lenovo T500) the problem is, that the brightness regulating key-press is applied twice - once by using the Xwindows, but also independently in the lower level, by kernel's graphic driver itself. So the brightness steps are twice as big as usual.

The working solution is to deny the low-level functionality, by adding this line to /etc/rc.local (just before the line with 'exit 0'):

echo -n 0 > /sys/module/video/parameters/brightness_switch_enabled

This way it will perfectly work in logged-in X session, unfortunately it will remove the key-press brightness regulation functionality in all other cases (console terminal, X login screen etc).

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This will give you amazing result (if it works successfully for you, of course)

sudo gedit /etc/default/grub

and make the replace the contents of the file by this one

 # If you change this file, run 'update-grub' afterwards to update
 # /boot/grub/grub.cfg.
 # For full documentation of the options in this file, see:
 #   info -f grub -n 'Simple configuration'
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

 # Uncomment to enable BadRAM filtering, modify to suit your needs
 # This works with Linux (no patch required) and with any kernel that obtains
 # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)

 # Uncomment to disable graphical terminal (grub-pc only)

 # The resolution used on graphical terminal
 # note that you can use only modes which your graphic card supports via VBE
 # you can see them in real GRUB with the command `vbeinfo'

 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux

 # Uncomment to disable generation of recovery mode menu entries

 # Uncomment to get a beep at grub start
 #GRUB_INIT_TUNE="480 440 1"

-------and then run sudo grub-update and then restart

by doing this i could lower my screen brightness to complete 0 like if the monitor was turned off.

[ credits : Vikas Malviya ]

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Wow, replacing all this file seems a little dangerous and will overwrite any difference between your setup and the user's setup. Did you actually mean to just locate the line with GRUB_CMDLINE_LINUX_DEFAULT and at the end add acpi_backlight=vendor ? – Stéphane Gourichon Jun 3 '14 at 20:12
I just booted an Asus n55s running Xubuntu 14.04 manually adding acpi_backlight=vendor on the linux line, and the only observable difference is the lack of the notification popup when I press the function keys. Brightness steps are the same size, xbacklight reads and writes same values as usual (steps of 10%). – Stéphane Gourichon Jun 4 '14 at 6:08
@StéphaneGourichon That'll be it. As documented elsewhere, on some hardware, that stops the BIOS & OS from both applying increments, which would reduce resolution by half. And yes, advising readers to overwrite their grub config is dangerous and a decidedly bad idea for a first post. – underscore_d Oct 18 '15 at 23:18

Hold down Ctrl while increasing/decreasing the brightness. Increases in steps of 1.

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