Nikon N65 Instruction Manual - Page 104

Focus Tracking, Focal length, Front-Curtain Sync, Guide number - 35mm film camera

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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-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 fI 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. 104

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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
=
--.::
.......
-------
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.
104