Hi JWH4480,
welcome to this Apple (user-to-user) Community!
Re: "iPhone/iPad screen brightness auto-adjusts, settings off"
Wondering if your iPhone and iPad are using the newest compatible iOS and iPadOS versions... keeping the OS updated often sidesteps issues.
You can check for updates in Settings > General > Software updates. (NB: Is always wise to back-up your iPhone and / or iPad
if you choose to update it's OS)
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Else: If already using the newest compatible software:
Wondering if you have tried restarting both your iPhone and your iPad:
(ie: Deletes temporary files, re-establishes connections, may update recent setting changes etc, and more. Often restores order when something is not working as you expect it to.)
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Re: "I went into all the automatic brightness settings. Turn them all off and it still happens. Where is the hidden setting? That’s causing this problem."
Apple support's online iPhone article (linked below) has lots of tips:
See: Adjust the screen brightness and color on iPhone - Apple Support
Eg: says:
"On iPhone, you can make your screen dimmer or brighter (dimming the screen extends battery life).
You can also adjust the screen brightness and color manually or automatically with Dark Mode, True Tone, and Night Shift".
See the linked iPhone article above for all the settings and how to adjust them:
Linked article below is for iPad:
Adjust the screen brightness and color on iPad - Apple Support
Hope this reply helps you take control of screen brightness again.
All the best :-)
