iPhone screen keep changing with auto brightness off

Have you tried turning off Settings>Accessibility-Display & Text Size>Auto-Brightness?

Also, if you use low-battery mode, that may affect it as well.

Thank you! I just got the phone yesterday and it has been awful with the brightness dimmed to dark every time the phone is put down and lifted up again! It was also yellow. I had turned off auto brightness and the night time thing and even did a reset. Nothing worked until now going to the accessibility and there it was! Why does Apple make lovely screens but then doesn’t want us to enjoy them??? The attached was what kept continuously!

Well if you are a person who often uses phone in direct sunlight, then dont turn off auto brightness as only auto brightness gives you the maximum brightness. Manual slider control wont give you the maximum yet. Donno why, but it is how it is

Glad it helped! I don't know why they hid that setting in Accessibility. As I recall, it used to be in the regular Display settings.

Thank you!