It's important to know just how your digital camera light meter works if you want properly exposed images. The metering system more or less controls the camera's aperture and shutter speed settings and it does this based on the ISO speed and the image's lighting conditions. The metering usually includes spot, evaluative zone or matrix, partial, and centre-weighted metering. All of these have lighting conditions that they excel at as well as those they fail at. It will help your end results if you understand these options.