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D-3
Appendix D
F-number
The numbers on the lens aperture ring and in the camera’s LCD that indicate the
relative size of the lens aperture opening. The f-number series is a geometric
progression based on changes in the size of the lens aperture, as it is opened and
closed. As the scale rises, each number is multiplied by a factor of 1.4. The
standard numbers for calibration are 1.0, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc.,
and each change results in a doubling or halving of the amount of light transmitted
by the lens.
Flexible Program
Flexible Program function temporarily shifts an automatically selected shutter
speed/aperture combination while maintaining correct exposure. That is, a desired
shutter speed or aperture can be selected in Programmed Auto exposure mode.
Focus-Priority for autofocus
The shutter cannot be released until the subject is in focus.
Focus-Priority is given to Single Servo AF mode while Release-Priority is given to
Continuous Servo AF.
Focus Tracking
Enables the camera to analyze the speed of the moving subject according to the
focus data detected, and to obtain correct focus by anticipating the subject’s
position—and driving the lens to that position—at the exact moment of exposure.
Focal length
The distance from the principal point to the focal point. In 35 mm-format cameras,
lenses with a focal length of approximately 50 mm are called normal or standard
lenses. Lenses with a focal length less than approximately 35 mm are called wide
angle lenses, and lenses with a focal length more than approximately. 85 mm are
called telephoto lenses. Lenses which allow the user to continuously vary the focal
length without changing focus are called zoom lenses.
Front-Curtain Sync
The flash fires an instant after the front curtain of a focal plane shutter has
completed its travel across the film plane. This is the way the F5 operates with the
flash sync mode at Normal Sync. See also “Rear-Curtain Sync.”