Auto-brightness skewed by apps

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19 points

Auto-brightness skewed by apps

Did anybody notice this?

This looks like a bug in the UIScreen.brightness API to me: According to the API spec any change of an app to the screen brightness through this API should be discarded after turning the display off and on again.

However, there are cases where brightness changes by apps have lasting effects on the auto-brightness curve. This affects iPhone 13 Pro Max with iOS 15.5.

Particularly ticket apps are changing the display brightness to display a ticket more clearly. (Examples: MVG, PayBack)

Steps to reproduce:

reset the auto-brightness using the toggle under Settings > Accessibility > Display & Text Size > Auto-Brightness
turn the display off
enter a room of medium brightness
turn the display on (brightness slider in the Control Center showing 30 to 40%)
turn the display off
go to a fully dark room
turn the display on (brightness slider showing 0%)
open one of the ticket apps
open a ticket (brightness going up to 100%)
close the ticket (brightness slider back at 0%)
(repeat it one or two times)
turn the display off
go to the previous room of medium brightness
turn the display on
the display is much darker now with the brightness slider showing 10 to 20%
the brightness curve won’t get back to normal until it’s reset again under Settings > Accessibility > Display & Text Size > Auto-Brightness

Best,

Alex

iPhone 13 Pro Max

Posted on Jun 29, 2022 01:18 AM

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Answer 1

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Alex5673 Author

Level 1

19 points

Jun 30, 2022 11:07 PM in response to Alex5673

This issue seems to be fixed for now after resetting all settings. (Settings > General > Transfer or Reset iPhone > Reset > Reset All Settings)

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Answer 2

Alex5673 Author

Level 1

19 points

Jun 30, 2022 12:54 AM in response to Alex5673

Actually, the above instructions help to reproduce the issue for some apps (e.g. MVG), but following slightly tweaked procedure works better for others (e.g. ZVV, PayBack):

reset the auto-brightness using the toggle under Settings > Accessibility > Display & Text Size > Auto-Brightness
turn the display off
enter a room of medium brightness
turn the display on (brightness slider in the Control Center showing 30 to 40%)
turn the display off
go to a fully dark room
turn the display on (brightness slider showing 0%)
open one of the ticket apps
open a ticket (brightness slider going up to 100%)
go to the previous room of medium brightness
close the ticket (brightness slider going back at 0%)
turn the display off
turn the display on (*)
the display is much darker now with the brightness slider showing 10 to 20%
the brightness curve won’t get back to normal until it’s reset again under Settings > Accessibility > Display & Text Size > Auto-Brightness

(*) I also tried it on an iPhone 13 mini and there seemingly all brightness changes applied by an app are properly deleted at this step, but not on my iPhone 13 Pro Max which consistently stays too dark after the described procedure.

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Auto-brightness skewed by apps

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