Ambient light sensor doesn't work as it supposed to.

If you take your iPhone 5 and take it next to a light source, the brightness screen will show it maxing the screen brightness out. But once you take the source away, the brightness does come down a few notches, but no where close to what it used to be before you introduced the light source ... is this normal? This creates a huge drain on my battery .. I have a case around it, but it comes no where close to the ambinet light sensor ... I also have a clear coat screen protector on it, but the area where the sensor is located, there is a cut out .. so that part is exposed....

but if you turn the screen off and turn it back on, it comes back to normal brightness settings... anyone else facing this issue?

Second issue.. if I shake my phone, I hear a slight rattle in it. I read through the forums about a "thud" noise, but this isn't a "thud" ... it's a rattle... any ideas?

-SK