Why does the brightness change by itself?

Question

Monitors

I have an Acer Nitro 5 laptop, the brightness changes by itself depending on what is happening on the screen.
If I turn on something light, then the brightness is high, if I turn on, for example, an application with a black theme, then the brightness, on the contrary, drops.
How to fix it?

Answer 1

Intel
Graphics Control Panel in Intel's proprietary utility, the item is called "display power saving".
AMD
VarBright
PS: even if this utility is not installed on Intel, the function still works, you need to install the utility, disable the function and you can remove the utility back)

Answer 2

See instructions. Most likely you have auto-regulation there.
Here is an example of settings
acerepair.ru/blog/kak-nastroit-yarkost-na-noutbuke-acer