Metering is a process which involves the camera taking a light level reading from the scene and selecting the appropriate combination of aperture and shutter speed to set the required exposure value. Various modes are offered to allow the user to select the most suitable one for the specific lighting conditions These can then be changed manually via use of exposure compensation metre if required. There are various types of metering which can be set, and these change the way the light levels are read by the camera.
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Spot metering
Spot metering takes a reading from a very small part of the image (between 1 and 5 per cent), and ignores the exposure of the rest of the scene. While this area is usually in the middle of the scene, some cameras allow the user to select a different part of the image from which to take a reading, or to recompose the shot after taking a reading. Spot metering is good choice for high contrast and backlit scenes but needs to be used with care, and aimed at an area that will form the mid-tone part of the final image.
