I have a new Canon Rebel K2 35mm camera. When I go into M mode, the exposure is at -2 no matter what I do to try to get it back to 0. None of the other settings (Av, Tv, etc.) have this problem - they are all at 0 and stay at zero. I don't know what I'm doing wrong to change the +/- - I'm following the manual's instructions and it says I set it to 0 but when I get back to the main screen and try to shoot, it blinks -2. Help!