How do I prevent iPhone from dimming brightness?

how do i prevent iphone from dimming brightness?

auto brightenss turned off.

reset phone

brightness at max.

accessibility feature for auto brightness also turned off and yet iphone will STILL dim in sunlight.

I also read that if iPhone gets hot it will dim… in the car with AC on and environment cold it STILL DIMS!

how do I stop this ?

[Re-Titled by Moderator]