Auto Brightness

Chances are you still have the slider way up high, so it will be bright. Auto brightness only adjusts the brightness relative to what you have set.

 

I noticed that if I turn the lights off and my iPhone is on then it doesn't adjust until I lock the screen and unlock it. Try that and see if it helps

 

Not sure why people would give the OP negative ratings... he has a point. The auto-brightness does not work nearly as well as it should, IMO. Also, often it comes on incorrect brightness and has to be turned off and back on (sleep)

 

If you have brightness set to full the auto-brightness doesn't do anything. try setting brightness to about 1/2 or 2/3 and see it that fixes your problem

 

Because the surface is glass, the brightness sensor can catch the reflections of other things in the background easily (e.g., the screen reflecting off of your glasses back at the phone's face). It's not full proof, but works decently well.

iOS's lack of dimming whenever you move from a light to a dark area was a purposed function. I think it was the original iPhone debut that Steve Jobs brought that up; he said something about it being awkward to be in a situation where the light was rapidly shifting and your phone was adjusting along with it, so the screen only brightens itself to stay readable in a high light situation.

 

However, it still doesn't work well. On my MacBook Pro for instance, the screen will dim and brighten from practically off, to all the way up to fully on, depending on the room brightness.
The iPhone has a very llimited range and I find that leaving it set to just above half way is necessary before the auto feature will use the full brightness in sunlight.
Wouldn't it be nice to set it at a MINIMUM brightness and then it could get brighter if it needed to?
That way, if you turn it on in the middle of the night, the screen will very dark (as soon as I switch it on!...why should I go half blind and unlock it at full brightness before it dims!?), until you need it to be brighter, at which point it does it automatically.
Makes sense to me, but then I'm odd I guess.

As far as rapidly shifting ambient light, let it adjust UP quickly and DOWN a bit more slowly...simple.

 

I end up having to do this with my iPad on occasion because it doesn't adjust as sensitively as I would like it to.