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GUIDE N U M B E R - - - - - - - - - - - - - - -
See the table below 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 modules
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
modu le or wi th
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 following
equation:
Usable
lis tops
-
guide number
at
full output
flash-to-subject
distance
guide
number at
1/16 output
flash-to-subject
distance
In
manual
flash
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 controller
AS-12
or AS-14 is turned on, the
controller ready-light
comes
on to indicate
flash
is
ready to
fire.
camera
meter
by
lightl
y pressing the shutte
r
release
button.
With alkaline-manganese or zinc-carbon batteries, if
the ready-light takes more than 30 sec. to light up,
replace batteries with a fresh
set.
To activate the viewfi nder ready-light
function when
us-
ing the Ni kon F4-series,
F-801
/N8008, FA,
FE
2,
F-501/N2020, F-301/N2000,
FG or
FG-20, turn on the
Ready-Light Warning Functions
To prevent errors listed
below,
the ready-lights inside the came ra'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.
Reset 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
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