Is that in 3D?
Asking because I get brighter pictures from 3D and darker in 2D with the settings the same.
In view mode there also seems to be a boost in brightness when changing from 2D to 3D, sort of flashes a moment.
Oh, and it could just be the Auto ISO setting you're dealing with there. Dark conditions is going to increase the exposure gain. You might try putting it on the lowest number for that, but of course it'll make pictures in the dark more... uh... dark.