Unlimited photographic versatility was the design concept adopted for the exposure control and TTL metering systems employed in the 645AF.

Three auto-exposure modes - aperture priority, shutter-priority and programmed - are backed up by full manual controls to provide versatile shooting options that suit any subject or conditions.

In programmed AE mode, the photographer can opt to shift exposure selection by +/-1.5 steps to accommodate an emphasis on faster shutter speed or smaller aperture.

Exposure metering is selectable between centre-weighted, spot and auto-selection mode, with three-image auto-bracketing available in steps of 1/3, 1/2, 2/3 or 1EV.

Basic exposure-compensation adjustment can be selected in 1/3 steps to a maximum of +/-3EV.