text: Typically , a fast shutter speed will require a larger aperture to ensure sufficient light exposure , and a slow shutter speed will require a smaller aperture to avoid excessive exposure .
simplified: Typically , a fast shutter speed will not let much light in ( meaning the picture could come out too dark ) , so the photographer will use a larger aperture to correct for this . A slow shutter speed will need a smaller aperture to stop the picture coming out too bright .