Same issue here. I live in Phoenix. Hike outside a lot. It could be 50 degrees out during winter, and with auto brightness turned off and all the other things support asks you to do, it still auto dims. Unable to see screen. While right clicking to ask Siri or just trying to find a solution, it will go to shutdown screen and emergency call and I can’t tell what I am doing, so several calls to 911. I turned that feature off. Not great for safety. I had this problem with my iPhone 6s Plus. I thought they would have a solution with their new expensive screen. I travel for several months a year. I go to a lot beaches and also mountain hiking, the phone is useless when it auto dims. I have no clue if I’m even touching the picture button and I for sure can’t change the settings of the shot. It doesn’t matter if it is first thing in the morning when it’s cool, case on or off. If it is bright outside it auto dims. Auto brightness is turned off. True Tone turned off. I spent $1,825 512 g and Apple care with theft protection. I’m in the apple ecosystem but this is an issue that is breaking the camel’s back.
This seems like an issue that Apple refuses to acknowledge or fix. They meaning Apple really bragged about the brightness of their screen. I have used other peoples phones hundreds of times while taking their pictures in Turkey, Greece, Thailand, and no issues with auto dimming on their phones. I also am not able to read any emails or do any work with this auto dimming issue.
Before I suggest all of us joining a class action suit against Apple on this, has anyone found a solution? Please none of the turn off and turn back on responses. Or check to see if auto brightness and true font is turned off. I would love to be shown a simple solution and proven that my thoughts about Apple were wrong on this. That they are not addressing this issue. Maybe there is an app out there that can help. Thanks. Rick