Trying to change brightness on my desktop screens via powershell and encountered an error

Question

Hello,

I want to change the brightness of my screens (I have two screens) on my desktop computer using PowerShell. I use this command:

(Get-WmiObject -namespace root/wmi -class WmiMonitorBrightnessMethods).wmisetvrightness(1,20)

and I get an error :

Get-WmiObject : Not supported
At line:1 char:2
+ (Get-WmiObject -namespace root/wmi -class WmiMonitorBrightnessMethods ...
+  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], ManagementException
    + FullyQualifiedErrorId : GetWMIManagementException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

You cannot call a method on a null-valued expression.
At line:1 char:1
+ (Get-WmiObject -namespace root/wmi -class WmiMonitorBrightnessMethods ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

I use the same command on my laptop and it works.

I would like to know why I get this error and how to fix it.

I know that my computer does not programmatically support changing the brightness and I know that there are free third-party programs that perform this operation, yet I want to understand how they do it and what command those programs use.

I ask because I want to build software that reduces screen brightness.

Answer 1

If you have 2 monitors, then the WMI call is probably returning 2 objects.

Try this.

Get-WmiObject -namespace root/wmi -class WmiMonitorBrightnessMethods | foreach {
    $_.wmisetbrightness(80,20)
}

Answer 2

I know that my computer does not programmatically support changing the brightness and I know that there are free third-party programs that perform this operation, yet I want to understand how they do it and what command those programs use.

It can be done with GetVCPFeatureAndVCPFeatureReply / SetVCPFeature

Brightness is 0x10 code (you can test codes with ClickMonitorDDC tool)

Answer 3

Are you running Windows Powershell 5, or the multi-platform PowerShell 7? WMI isn't part of PowerShell 7.