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GUIDE
NUMBER---------------
See
the table
be
low for guide numbers.
Guide
number
at
flash-to-subject distance
of
1 m
(approx
. 3.3 ft.)
Unit:
m(ft.)
Amount
of
light output
ISO
film
speed
in
M
mode
25
50 100 200
400
800
1000 1600
For both flash modul
es
6.5 9
13 18
26
36
41
52
with controller batteries
(21)
(30) (43) (60) (85) (120)
(135)
(171)
Full
For only one flash
7.5
11
15
21
30
42 48
60
module or with external
(25) (35)
(49) (69) (98) (139) (156) (197)
power
source·
1/4
3.2 4.6 6.5 9
13
18
21
26
(10)
(15)
(21) (30) (43) (60) (68) (85)
1/16
1.6 2.3
3.2 4.6 6.5 9
10 13
(53)
(7
.5)
(10)
(15)
(21)
(30)
(34) (43)
• For external power source with only one flash module, see the figure indicated
in
the column
to
the right (column for one step
higher film speed)
In TTL auto flash operation, for usable apertures with a
reproduction ratio lower than
1:
10
, use the
fo
ll
owing
equation:
Usable
lis tops -
guide number
at
full output
flash-to-subject
distance
guide number
at
1/16
output
flash-to
-s
ubject
distance
In manual fl
ash
operation, for usable aperture with a
reproduction ratio lower than 1:
10
, use the following
equation:
guide number
Usable flstop
=
--=---------
flash-to-subject distance
READY-LIGHT
INDICATIONS-----------
When the contro
ll
er
AS-
12
or
AS-14
is
turned
on,
the
controller ready-light comes
on
to indicate flash
is
ready to fire.
camera meter by lig
htl
y pressing the shutter release
button.
Wi
th alkaline-manganese or zinc-carbon batteri
es,
if
th
e
rea
d
y-
li
ght takes more than 30 sec. to
li
ght
up,
re
pl
ace batteries with a fresh set.
To activate the viewfinder ready-light function when u
s-
ing the
Ni
kon F4-series, F-
801
/N8008, F
A,
FE
2,
F-501/N2020, F-301/N200
0,
FG
or FG-20, turn on the
Ready-Light Warning Functions
To
prevent errors listed below, the ready-lights inside the camera's
viewfinder
and
on
the controller blink, after the
S8-21
is
turned
on.
With
SB
-
21A
Blinking
ready
-light
Inside
On
AS·12
Problem
and
remedy
viewfinder
1)
The
AS
-12's mounting foot
is
not securely locked. Firmly tighten lock ring.
2)
The
AS
-
12
is
set at TTL with a camera other than a Nikon
F3
-series camera.
Re
se
t flash mode selector to M.
0 0
3)
In
TTL mode, the film speed setting
on
the camera
is
beyond the usable range.
Use film within range
of
ISO
25
to 400.
4) The flash fired at full light output
in
TTL mode; lighting might
be
insufficient.
(See page 37).
0 -
The shutter speed set
on
the FM2 or
FE
is
faster than the flash sync speed. Reset to
flash sync speed or slower.
40