A built-in exposure meter is a component inside a camera that measures the amount of light in the photographed scene. Based on this measurement, it helps the camera or the photographer directly to set the correct exposure, which is the total amount of light that hits the sensor and affects the final brightness of the image. Exposure is controlled by a combination of three values: aperture, shutter speed, and ISO sensitivity. In manual mode, the camera displays the exposure meter readings, typically on a scale in the viewfinder or on the display, and the photographer manually adjusts the settings accordingly. In automatic and semi-automatic modes, the camera's automatic system directly uses this information to independently set one or more of these values to achieve a balanced photograph.
