When I shoot in program I'm often getting underexposed shots. I've been shooting in raw lately so I've been able to adjust the exposure afterwards but I want to get it right in camera. I'm guessing part of my issue may be what metering style. I've got 4 possibilities with my camera. Can anyone explain the difference? I read the manual but I'm still a bit confused. My 4 possibilities are evaluative, partial, spot & center-weighted average.