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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-Curta
in
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:
I
guide number
f stop
=
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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
=
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f/stop
Useful for determining the maximum flash-to-subject distance for flash
photography.
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