Automatic exposure

The Automatic mode of the camera determines the optimal combination of aperture, shutter speed, and sensitivity based on the exposure value determined by the camera light metering system. The camera’s microcomputer usually assumes that you want to take a picture using the fastest available shutter speed because this minimizes camera shake and the blur that can result from a moving object.

Automatic mode does poorly in the following situations:
  • There is little or no contrast between the subject and the background (i.e., the subject is the same color as the background)
  • The subject is dominated by regular geometric patterns, such as a row of windows in a building
  • The focus area contains areas of sharply contrasting brightness, such as when the target is halfway in the shade
  • The subject contains many fine details, such as a field containing patches of snow or light-colored soil or rock
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