I know this is probably a dumb question, but why hasn't anyone made photochromic lenses for headlights or windows yet? That's the stuff that automatically makes your glasses darken in the presence of UV. It seems obvious to me that someone should make this. When something seems obvious to me but doesn't exist, there's usually a stupid reason I didn't think of that makes me look foolish. Anyway, anyone have any input? I mean, that would make all our tinted lighting needs look like we want without losing light output at night, etc.