[SOLVED] How do I adjust screen brightness on an Asus G750JS?

[m654321]

The screen brightness appears to be fixed (at maximum level) on the Asus G750JS with LL2.4.  I would like to be able to adjust the brightness, e.g. dim it.
The fn key + f5 or with f6 doesn't appear to work, neither does fn + arrow keys.

Any help on this one much appreciated.

Regards
Mike

[anon222]

What is the output of

Code:

xrandr

When I run xrandr I get this:

Code:

xrandr
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
DVI-I-0 disconnected (normal left inverted right x axis y axis)
VGA-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080      60.0*+
   1680x1050      60.0 
   1280x1024      75.0     60.0 
   1152x864       75.0 
   1024x768       75.0     60.0 
   800x600        75.0     60.3 
   640x480        75.0     59.9 
DVI-I-1 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)

Loook for the word connected in the output. Whatever stands in front of it is the port yout monitor is conected to.
For me it's VGA-0
To change the brightness toi 70% I use this command

Code:

xrandr --output VGA-0 --brightness 0.7

And to return to normal

Code:

xrandr --output VGA-0 --brightness 1

As you see the value goes from 0 to 1.

If you are not sure how to do this and you have only one monitor connected, use this command:

Code:

xrandr | sed -n 's/ connected.*//p' | xargs -n1 -tri xrandr --output {} --brightness 0.6

It will run xrandr, find the line containing string connected and remove that string and everything behind that. What's left it will be passed through the pipe and and the brightness will be set to to 0.6
To change it back use

Code:

xrandr | sed -n 's/ connected.*//p' | xargs -n1 -tri xrandr --output {} --brightness 1

You can set the keyboard shortcuts to run these commands
Menu -> Settings -> Keyboard -> Application Shortcuts <-

You can also set gamma while setting the brightness
The colors are 1:1:1 meaning red:green:blue all set to 100%

Code:

xrandr | sed -n 's/ connected.*//p' | xargs -n1 -tri xrandr --output {} --brightness 0.6 --gamma 0.1:1:1

To change it back.

Code:

xrandr | sed -n 's/ connected.*//p' | xargs -n1 -tri xrandr --output {} --brightness 1 --gamma 1:1:1

[m654321]

Many thanks misko_2083 for the detailed post you made on May 16.  What I wanted was to use the same key combinations to change the brightness of the backlight controller in LL (in a variable rather than fixed fashion), as used for win8.1 on the laptop mentioned, i.e...

• Fn+F5 - decrease brightness
  
• Fn+F6 - increase brightness
  

A  brightness scale will appear in the top right hand of the screen when either key combination is used.  On the net I found the following solution which works excellently (I have misplaced the reference for the original source)...

In order to get the Fn keys working, "acpi_osi=" needs to be inserted into the file    /etc/default/grub.  This will enable support of the Fn keys and, apparently, works for the newer Asus laptops.  For LL, you may need to first install gedit  from the synaptic package manager (install/remove software choice in menu) as this does not appear to be installed in thedownloaded iso file by default.  When gedit is installed, open the terminal and type the following code...

Code:

gksudo gedit /etc/default/grub

The etc/default/grub file will then open on your screen. Then look for this line in the file and make the change:

Code:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to...

Code:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi="

then save and run...

Code:

sudo update-grub

On reboot the Fn+F5 and Fn+F6 brightness keys will function.
Regards, Mike

[anon222]

Cheers mate.
Gedit is a fine text editor but any will do. In LL leafpad is the default text editor

Code:

gksudo leafpad /etc/default/grub

would do the same as

Code:

gksudo gedit /etc/default/grub

So disabling all the strings with that kernel boot parameter gets Fn keys working?

[avj]

As a note if you don't have a manual for this computer it can be found here: 
https://www.asus.com/Notebooks/ASUS_ROG_...sk_Manual/

[m654321]

Thankyou misko for the tip about using either leafpad or gedit as a text editor - didn't know that - I'm learning all the time...

Thankyou avj  re. ROG manual - do you have an Asus G750? How do you find it?  I do have the manual, though didn't think to look there re. problems with Linux installations generally or backlighting issues specifically - maybe I should take a browse...

Regards
Mike 

[avj]

I am using an Acer netbook, but I recommend that you always keep the manual that comes with your computer. If you didn't get a manual most can be found by google searching the brand and model number, IE: "Asus G750JS manual".  Most manufacturers have a download page for manuals. When you search look for links to the manufacturers website.

Hopefully that will be helpful to others as well.

[m654321]

avj - I already have the manual - yes, definitely advisable to keep this, though as you say they can usually be found online.  However, unsurprisingly, I haven't found a manual as  yet that mentions Linux operating systems, certainly not for Samsung or Asus at any rate ... oops - I'm going off topic here...

Regards
Mike

[avj]

As another side note it occurs to me that this might be a side effect of a misconfigured keyboard layout. IE: "Asus Laptop" layout instead of system default.

[Wirezfree]

Just a comment on a similar situation with a "HP TS-15 Laptop"
My Brightness did not work with the FN+F2 & FN+F3 keys.

I found a fix with modifying the grub line to:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"