Light spot when brightness is all the way down

[eta90]

When I turn my brightness all the way down, there's still a barely (but clear, still) lit circle at the centre of my screen. I have a 13'' mbp. I can even see my cursor and move it around. This spot, at very low screen brightness, appears kind of yellowish. When I turn the brightness up, it is not noticeable. The circle part has roughly a two inch diameter.

I've had the mbp for about a month, and just noticed this now. I do turn my brightness down quite a bit, but its usually in a well lit classroom and thus its possible I just did not notice this circle that is still barely lit until now.

Anybody have any ideas? Should I take it to the Genius Bar?

UPDATE*: I have just discovered that covering the lit apple logo on the screen's exterior (directly opposite the lit circle i suppose) causing the circle to gradually disappear. THe laptop is sitting behind a window (ie light can shine on that apple logo)...what's up with this?

 

[iBryton]

Yes you should call Apple first if a Genius bar is far for you.

 

[DewGuy1999]

An LCD allows light to shine through from behind to illuminate it, this is achieved with backlighting from either fluorescent lights or LEDs. Since the MacBook Pro has a translucent Apple on the back of the display, this allows bright light to shine through it and illuminate the LCD display. The inverse of this is that the backlighting for the LCD display is what provides the illumination of the Apple.

 

[Merkava_4]

If you have your computer completely off, and you have the back of the
display facing the bright sunlight, you'll see a white Apple on the screen.