Why does the screen darken and brighten when switching windows?

Question

Monitors

When switching between programs (win10), the screen either brightens a little, then darkens a little. And not always. Even within the same program, when viewing a photo gallery, somewhere the brightness is enhanced, somewhere not. It interferes with design.
What is the reason for this phenomenon? The power settings are set to maximum speed. There is nothing in the monitor settings that looks like adaptive brightness control. And in Windows I did not find anything similar.
What could it be?

Answer 1

The battery and power supply settings can also look in the items for screen brightness or just the screen.