I'm a newbie, so I have a couple basic things that I was hoping could be clarified here: The aperature can be used to control light, as can the shutter speed... is there any time when I'd actually want to raise the aperature number rather than adjust the shutter speed? Would this decrease the depth of field or something? Light meters - good to have? I hate using auto settings, but I always end up taking multiple test shots on different settings before I find one that handles the light correctly. Would a separate light meter help me with this? Is that what they do? Thanks in advance.