Automatic meter
From The Glossary of Digital Photography
A meter built in to the camera that has control over the aperture and/or the shutter speed when setting exposure. The meter reads the light reflected from the subject and sets it approximately to an 18% gray level to create a proper exposure. This automatic meter function can be set so that it creates an automatic exposure by adjusting both the aperture and shutter speed, locks in a shutter speed at one value and adjusts the aperture, or locks in the aperture at one value and then adjusts the shutter speed. The automatic function is usually user selectable. Often, the automatic function can be turned off or adjusted in increments for situations in which the subject is not an 18% gray level, such as a portrait of a bride in a white wedding dress. In that case, the exposure can be adjusted by increments of 1/2 or 1/3 stop so the automatic feature will still operate. See also 18% gray; exposure compensation
