One of the advantages of owning an iPhone is its ability to
adjust the screen intensity depending on the current
environment. Unfortunately, this auto-brightness feature has
been known to be a little bit clunky at times, especially on the
iPhone 5.  If your auto-brightness isn’t working on your
handset, here is how to fix it, courtesy of iMore.    1. Go into
a dimly lit or dark room.   2. Launch the Settings app from the
Home screen of your iPhone/iPod touch or iPad   3. Tap on
Brightness & Wallpaper.   4. Turn the auto-brightness setting to
Off.   5. Adjust the brightness slider to the level you would
like your screen brightness to be at in the given environment.
For instance, if you’re in a completely dark room, you’ll
probably want to put the slider all the way to low or pretty
close to all the way down.   6. Turn the auto-brightness setting
to On again.   7. Now flip on a light switch.  Here is the
video:  Assuming that the brightness slider is now moving on its
own, you have successfully re-calibrated th