Perfect dimmer for dark surroundings. Use it all the time! I have it on auto dim  great feature! UPDATE 1/1/17 dropped 2 stars  new update has messed it up. It no longer stays on even though lock screen says it's on and at desired setting . When phone is unlocked  it shuts off and it has to be turned on again. Its really annoying at night. I really wish I never updated. It worked perfectly. Please fix! 2/8/17- still not fixed  3/30/17 dropped another star  still not fixed