The 645AF employs a data-imprint function that can be activated to print various data outside the image area of the film.

Data mode enables imprinting of exposure mode, aperture, shutter speed, exposure compensation, metering mode and three-digit ID number; Day mode provides year/month/date/time and ID number.

The ID number is also stored in memory in the camera body, with the count continuing even when film magazines are changed; this is useful for managing large volumes of film in studio or location shoots.

The counter can be set to start at any number (001-999) for additional versatility in classifying images.