How to disable automatic display brightness?

I often change power plan or (dis)connect the power cord depending on what I do with my laptop and where I am. Every time I do so, the display brightness changes into whatever it was last time I had the same power plan and AC power status.

The display brightness has nothing to do with those settings. I adjust it manually to what I feel comfortable with in the current environment, and it's frustrating having it changed by some automatic setting that gets it wrong every time.

I'm in a dark room, getting ready to watch a movie or something, everything set perfectly. Oh right, the power cord. Boom, instant 20% to 100% flash that kills my eyes. Thanks Microsoft...

How do I disable this automatic adjusting and get full control over the brightness?

Hello and welcome to the board.

The "automatic adjusting" is triggered by the Adaptive Brightness Service which
"Monitors ambient light sensors to detect changes in ambient light and adjust the
display brightness. If this service is stopped or disabled, the display brightness will
not adapt to lighting conditions."

So, disabling the service will prevent the auto-adjustment and resolve your frustration.

Start > Run. Type 'services.msc' (without the quotes) and hit Enter.

Right-click on 'Adaptive Brightness' and select Properties. Set the start-up type to: Disabled.

I'm sorry but that didn't change anything. I mean, it seems to be about some kind of light sensor in the computer (which mine doesn't even have I think), and not the power plans.

My problem is that the different power plans have their own idea of how bright my display should be, while they should have nothing to do with it. I want to completely disconnect the brightness controls from them, and have total manual control over it. It should never change unless I want it to.
Whether I change the power plan myself, or plug/unplug the power cord, the brightness should never change unless I specifically change it myself (keyboard shortcut or otherwise).