Brightness temperature

[sarasphotobox]

Not sure whst this feature is shall I keep it standard or light 

S25 base model 

[Tourbillon De La Vie]

sitting on bench on a hot sunny day browsing on the phone. As the phone heats up it will reduce brightness after awhile to help reduce the heat. Or continues at full brightness 

[sarasphotobox]

Ok so what option is better