How can I stop my iPhone 15 Pro brightness Changing automatically?

I have an iPhone 15 Pro and I noticed, on social networks, that the brightness changes by itself and some pictures appear to be brighter than the rest of the screen; for example on Instagram or TikTok the video or picture is brighter than the caption or the comments. Even if my brightness is all the way down the videos still look super bright. I already turned automatic brightness off, true tone off, night shift off.

Thanks everybody

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