Nikon 1718 Instruction Manual - Page 108

Glossary-continued

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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. 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 N55 operates with the flash sync mode at Normal Sync. Guide number The guide number indicates the power of a flash in relation to ISO film speed. The guide number of the built-in Speedlight of the N55 is 12 (ISO 100, m). 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: flash-to-subject distance =-g-ui-de-nu-mb-er f/ stop Useful for determining the maximum flash-to-subject distance for flash photography. ISO film speed The international standard for representing film sensitivity. The higher the number, the greater the sensitivity, and vice versa. A film speed of ISO 200 is twice as sensitive as ISO 100, and half that of ISO 400 film. 108

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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.
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 N55 operates with the flash sync mode
at Normal Sync.
Guide number
The guide number indicates the power of a flash
in
relation
to
ISO
film speed. The guide
number
of
the built-in Speed light of the N55 is
12
(ISO
100,
m)
. 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.
ISO film speed
The international standard for representing film sensitivity. The higher the number, the
greater the sensitivity, and vice versa. A film speed of
ISO
200 is twice
as
sensitive
as
ISO 100, and half that of ISO 400 film.
108