My iphone 5 went from being bright screen to very dim and barely seeable?

Yesterday i was in the doc office and my iphone 5 screen was decent bright not fully and when i put it down it went very dim for no reason?

Mines done that before, i just turned it off and on and it worked. If not try resyncing. Hope this helps x

Go to settings, scroll down and click on brightness and wallpaper, then turn your auto brightness up

Settings>brightness and wallpaper (iOS 6)> set your preferred level>turn off auto brightness

Goto your settings and look for "Brightness* and move the ball on the line all the way to the right.