Full-Aperture Metering

DEFINITION:

The TTL metering system which measures brightness with the diaphragm fully opened.

DESCRIPTION:

Full-aperture metering can keep the viewfinder bright and because of this feature, most TTL single-lens reflex cameras now use this system.

The full-aperture metering system consists of the following functions:

1. To stop aperture down to the selected value at shutter release.

2. To check the maximum aperture of lens mounted.

3. To determine the correct exposure based on the selected aperture of lens.

4. To display the correct exposure as determined above, and to control shutter speed in the case of an AE camera.