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I have a Sony Vaio laptop, and it runs windows 7. I know I can adjust screen brightness from the control panel, but I want to force it to be even brighter. Is there a hack, or a way to do this from command prompt?

5
  • Do your Fn + <key> brightness controls not work?
    – kobaltz
    Sep 9, 2012 at 21:27
  • There's a powercfg command that allows you to change the values of the brightness index but it's used for specific themes (Ex. -SETACVALUEINDEX is used when the computer is plugged in). I don't believe this is what you're looking for...
    – Rob
    Sep 10, 2012 at 0:31
  • I guess there aren't any parameters for powercfg.cpl... good question +1. I was wondering the same thing about adjusting the speed of the fan through command prompt.
    – Rob
    Sep 10, 2012 at 0:32
  • Your title seems to ask a different question that the description - if you're just after a way to increase screen brightness, there is a hack for a Sony laptop here but I'm not sure if this will work forum.notebookreview.com/sony/…
    – Dave
    Sep 10, 2012 at 12:13
  • I would use something like Process Monitor and see if any registry settings were changed when you use the control panel applet. you can then use reg to read/set registry keys from the command line
    – SeanC
    Sep 11, 2012 at 13:28

2 Answers 2

17

OK, so here's what I did:

The two commands for setting any power settings are powercfg -SetDcValueIndex and powercfg -SetAcValueIndex, depending if you want to change setting when on batteries or on AC power. This command has format (case insensitive):

POWERCFG -SETDCVALUEINDEX <SCHEME_GUID> <SUBGROUP_GUID> <SETTING_GUID> value

Then we need three GUIDs. Find them by running powercfg -q. The output looks like this (it will be in your system's language):

D:\Users\212579988>powercfg /q
Power Scheme GUID: 381b4222-f694-41f0-9685-ff5bb260df2e  (Balanced)
  Subgroup GUID: fea3413e-7e05-4911-9a71-700331f1c294  (Settings belonging to no subgroup)
    Power Setting GUID: 0e796bdb-100d-47d6-a2d5-f7d2daa51f51  (Require a password on wakeup)
      Possible Setting Index: 000
      Possible Setting Friendly Name: No
      Possible Setting Index: 001
      Possible Setting Friendly Name: Yes
    Current AC Power Setting Index: 0x00000001
    Current DC Power Setting Index: 0x00000001

  Subgroup GUID: 0012ee47-9041-4b5d-9b77-535fba8b1442  (Hard disk)
    Power Setting GUID: 6738e2c4-e8a5-4a42-b16a-e040e769756e  (Turn off hard disk after)
      Minimum Possible Setting: 0x00000000
      Maximum Possible Setting: 0xffffffff
      Possible Settings increment: 0x00000001
      Possible Settings units: Seconds
    Current AC Power Setting Index: 0x00000000
    Current DC Power Setting Index: 0x00000000

...

  Subgroup GUID: 7516b95f-f776-4464-8c53-06167f40cc99  (Display)
    Power Setting GUID: 17aaa29b-8b43-4b94-aafe-35f64daaf1ee  (Dim display after)
      Minimum Possible Setting: 0x00000000
      Maximum Possible Setting: 0xffffffff
      Possible Settings increment: 0x00000001
      Possible Settings units: Seconds
    Current AC Power Setting Index: 0x0000012c
    Current DC Power Setting Index: 0x00000078

    Power Setting GUID: 3c0bc021-c8a8-4e07-a973-6b14cbcb2b7e  (Turn off display after)
      Minimum Possible Setting: 0x00000000
      Maximum Possible Setting: 0xffffffff
      Possible Settings increment: 0x00000001
      Possible Settings units: Seconds
    Current AC Power Setting Index: 0x00000258
    Current DC Power Setting Index: 0x0000012c

    Power Setting GUID: aded5e82-b909-4619-9949-f5d71dac0bcb  (Display brightness)
      Minimum Possible Setting: 0x00000000
      Maximum Possible Setting: 0x00000064
      Possible Settings increment: 0x00000001
      Possible Settings units: %
    Current AC Power Setting Index: 0x00000064
    Current DC Power Setting Index: 0x0000000c

...

Now you need to find and write down:

  • current scheme GUID - it's in the first line.
  • subgroup GUID for Display - look down for Display
  • setting GUID for brightness - look down for Display Brightness

Now put your three GUID values plus desired brightness in percent - lets say 10% - like this:

C:\Users\Mike>powercfg -SetDcValueIndex 381b4222-f694-41f0-9685-ff5bb260df2e 7516b95f-f776-4464-8c53-06167f40cc99 aded5e82-b909-4619-9949-f5d71dac0bcb 10 

And... nothing happened for me! The brightness didn't change! By executing powercfg /q I checked that indeed my new value was stored properly. So I just asked to make my power setting active (even though it was active all the time):

C:\Users\Mike>powercfg -S 381b4222-f694-41f0-9685-ff5bb260df2e

And voila! my screen brightness dimmed to 10%!

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  • Nice first post!
    – slm
    Dec 29, 2012 at 16:08
  • 4
    Great post here. Some clarification: For English, the current scheme is referred to as Power Scheme, the subgroup GUID for screen settings is labeled Display and the setting GUID for brightness is labeled Display brightness. The following command will get all the necessary data for you: powercfg -q | find "Power Scheme GUID" & powercfg -q | find "(Display)" & powercfg -q | find "(Display brightness)"
    – Iszi
    Jun 7, 2013 at 16:25
  • I tried this and it didn't work. Might it need to be run from an elevated command prompt?
    – Iszi
    Jun 7, 2013 at 16:39
  • I think I figured out my problem. It looks like this won't work if your settings are locked down by GPO.
    – Iszi
    Jun 7, 2013 at 17:09
  • 3
    On Windows 7 and newer there are aliases for most of the GUIDS, you can use the /Query option as shown in the post and look for Friendly name. And you can also use /Aliases to list most of the aliases in a nice hierarchical table. Unfortunately there is no alias for the brightness, only for the video sub section. There are also friendly names for the built in schemes, most notably the current active scheme SCHEME_CURRENT, and all schemes SCHEME_ALL (undocumented?). So the above command becomes: powercfg -setdcvalueindex SCHEME_CURRENT SUB_VIDEO aded5e82-b909-4619-9949-f5d71dac0bcb 10
    – nohwnd
    Nov 7, 2018 at 13:53
9

I made a batch file that works for english which uses the method above. http://aarongiera.com/change_brightness.bat

for /f "tokens=*" %%i in ('powercfg -q ^| find "Power Scheme GUID"') do set pwrSchm=%%i
set pwrSchm=%pwrSchm:~19,36%

for /f "tokens=*" %%i in ('powercfg -q ^| find "(Display)"') do set dsply=%%i
set dsply=%dsply:~15,36%

for /f "tokens=*" %%i in ('powercfg -q ^| find "(Display brightness)"') do set brtnss=%%i
set brtnss=%brtnss:~20,36%

set /P brightness=Enter % brightness:  %=%

powercfg -SetDcValueIndex %pwrSchm% %dsply% %brtnss% %brightness%
powercfg -S %pwrSchm%

It works, but only on a scale of 0-100. It can't any lower or higher brightness the leds are capable of disappointingly.

2
  • Hi @user2089636, please you can share the bat on OneDrive or Mega or other server shared? The link that you posted is outdated (you site is offline) Mar 21, 2017 at 8:41
  • This uses specifically the setting for when the laptop is on battery: -SetDcValueIndex and not -SetAcValueIndex (on adapter power). Here is how to choose the value for the current situation: set AcDc=Dc WMIC /NameSpace:\\root\WMI Path BatteryStatus Get PowerOnline | find /i "true" > nul && set AcDc=Ac powercfg -Set%AcDc%ValueIndex SCHEME_CURRENT SUB_VIDEO %brtnss% %brightness%. May 6, 2019 at 14:39

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