Default strange brightness intensity

Hello all,

Sometimes when I am on web page or simply surfing facebook and my Note 3 dimms after 15 seconds as set, when I touch the screen, brightness will go lower as it has been set..Than I wait untill it dimms again, touch the screen and it goes to set level.. It happens either when on autobrightness (i am not moving phones position) or when all features controlling screen brightness are off (screen mode auto adapt, automatic tone adjustment, auto brightness, power saving options etc..) No third party app controlling brightness is installed.