Nikon n65 - Manual (Page 104)

Glossary—
continued
Focus Tracking
Enables the camera to analyze the speed of a moving subject according to the
focus data detected, and to obtain correct focus by anticipating the subject’s
position—at the exact moment of exposure.
Lock-On^“ Autofocus keeps focus firmly on a main subject during Focus Tracking
even if some other object momentarily blocks it in the viewfinder.
Focal length
The distance from the principal point to the focal point. In 35mm-format cameras,
lenses with a focal length of approx. 50mm are called normal or standard lenses.
Lenses with a focal length less than approx. 35mm are called wideangle lenses,
and lenses with a focal length more than approx. 85mm 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 N65/N65QD operates
with the flash sync mode at Normal Sync. (See “Rear-Curtain Sync”.)
Guide number
The guide number indicates the power of a flash in relation to ISO film speed.
Guide numbers are quoted in either meters or feet. Guide numbers are used to
calculate the f/stop for correct exposure as follows:
guide number
f/stop =-----------------------------------
flash-to-subject distance
Using a selected aperture, we can calculate the required flash-to-subject distance
with the formula:
guide number
flash-to-subject distance =-----------------------
f/stop
Useful for determining the maximum flash-to-subject distance for flash
photography.
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