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I
In
manual mode. you can determine the correct flstop using the following
equation:
flstop
=
__
-"g_
ui
_d_e_n_um_ b_er
__
flash
-t
o-subject distance
See table below for the guide number at various film speed.
Guide
number
at
various film speed
Light
Underwater shooting
output
18025
50
64
100
200
400
M Full 8 (26)
11
(36) 12 (39) 16 (53)
22 (72)
32 (105)
M 1/4 4 (13) 5.6 (18) 6 (20) 8 (26)
11
(36) 16 (53)
M 1/16
2 (7) 2.8
(9)
3 (10) 4 (13) 5.6 (18) 8 (26)
Light On-land shooting
output
18025
50
64
100
200
400
M Full 16 (52) 22 (72) 25 (82) 32 (105) 45 (148) 64 (210)
M 1/4 8 (26)
11
(36) 12 (39) 16 (52)
22 (72)
32 (105)
M 1/16 4 (13) 5.6 (18) 6 (20) 8 (26)
11
(36) 16 (52)
_ Caution
- Guide numbers under water vary according to water conditions.
- When aiming the Speedlight diagonal
ly.
open the aperture 1/2 to 1
800
45 (148)
22 (72)
11
(36)
800
90 (295)
45 (148)
22 (72)
step wider (smaller f-number) than the aperture value obtained
in
the
above equation to compensate for the different angle
of
reflection.
_When taking photographs with the arm removed from the bracket.
Nikon recommends you to take various pictures with different
apertures by adjusting the camera-to-subject distance .
• Important
If the camera-to-subject distance is actua
ll
y measured underwater.
multiply the measured distance by
3/4 to get the estimated distance
underwater.
For example. if the actual camera-to-subject distance is 1.33 meters
(4.3 feet). set the lens distance scale to 1 meter
(3
.3 feet). and read the
"1 meter" column on the exposure calculation chart.
44
m (ft)
1000
50 (164)
25 (82)
12 (39)
m (tt)
1000
101
(331)
50 (164)
25 (82)