This is a completely uninteresting post, but I hope this will be useful for people trying to figure out how to adjust screen brightness in Bootcamp. It took me far too long to search for this answer, and I ended up having to figure it out myself.
If you dim your screen on OS X and then boot into Windows, you end up with a darkened screen. The F1 and F2 keys that normally adjust brightness do not work in Bootcamp.
What you can do is go to Control Panel > Boot Camp > Brightness. Even if the slider is showing it’s on brightest, slide it all the way down to darker and back up. It should make the screen nice and bright. Hopefully that helps.