Cameras and exposure meters can take readings of the light levels in a number of ways, from basic to advanced methods. The most basic is Centre-weighted (CW) or average metering that takes a measurement from most of the image area. A more sophisticated version of this is Partial (P) metering that has a narrow area of measurement that is still based on the centre of the image and Spot (S) that can measure from as little as 1 of the image. The most commonly used in more advanced cameras now is Matrix, also known as Multi-pattern (MP) or segment metering, that takes readings from several parts of the scene and produces a calculated average. In most cases the basic metering with an auto camera is fine, especially if you have the sun behind you or it is overcast. But when you start to try more advanced shots, such as the sun behind the subject for a backlit halo effect or an archway with light streaming through the pillars or a spotlit subject against a dark background, you may find the standard meter will let you down. If you can see yourself shooting subjects like this, buy a camera that lets you switch over to spot or multi-pattern metering.