iPhone brightness dims even if the setting is set to max brightness

nona64 wrote:

Thank you for clarifying. I thought it would be something like that, but its terribly annoying so I hoped there was a way to turn it off, but I assume there’s not if its a safety feature, right? :p

Correct. There is no way to turn it off.

As per this Support Article, If your iPhone or iPad gets too hot or too cold - Apple Support

"Avoid these conditions and activities because they might change the performance of your device:

• • Leaving your device in direct sunlight for an extended period of time.
  • Using certain features in hot conditions or direct sunlight for an extended period of time, such as GPS tracking or navigation in a car, playing a graphics-intensive game, or using augmented-reality apps.

If the interior temperature of your device exceeds the normal operating range, you might notice these changes:

• • The display dims or goes black.

If this happens you should move your device away from direct sunlight into someplace shady.

This is actually a safety feature where your iPhone can automatically dim it's brightness even at full level if it's exposed to sunlight. This is to conserve battery power and prevent overheating, as heat is not good for an iPhone's battery longevity.

But in addition check the battery health provided by H1290. If your iPhone is running on a significantly degraded battery it can cause it to lower its brightness.

nona64 wrote:

81%, while I know thats not the best, apple still tells us its functional so I didn’t expect these kinds of effects to occur

Apple suggests you replace the battery at 80%, which at that point is considered a significantly degraded battery. That can also cause the brightness to dim, and by getting it replaced, it may not dim as much.

Genius Bar Reservation and Apple Support Options - Apple

nona64 wrote:

81%, while I know thats not the best, apple still tells us its functional so I didn’t expect these kinds of effects to occur

Yeah like Zachy said, an older battery can cause this to happen. This can (and will) also happen on devices where the battery has significantly drained (less than 20%). So just try not to let the battery get too low before charging it.

Hello!

What is the Maximum Capacity of the device’s battery? You’ll find it in: Settings > Battery > Battery Health & Charging.