need a crash course here to jog my memory: how do i obtain a good exposure for a certain given situation i.e.: if i want to take the city scape at night (with an illuminated monument a la fullerton at night against the dark night sky, or cars on the road against the night sky); candlelight in the night; bright sunny sky with my subject being very dark, say, a black car? or just simply, a cloudy day? do i just let my camera metre at the sky and adjust the exposure accordingly? how will it affect the exposure for the bright and dark areas? am i to assume that regardless of the situation my camera gives the idealised exposure settings? if i use iso 100 or iso 400 and then the built-in meter on my camera, how'd it affect my exposure settings? also, what good are polarising filters? thanks!