Nikon Autofocus Speedlight SB-20 - Guide Number

Guide Number
See the table
at
right
for
guide
numbers
of the film
speeds and zoom
settings.
In M mode,
use the following
equation
to determine
aDerlure:
f/stop
-
guide
number
f lash-to-subject
distance
With ISO 400
film
and the zoom
set knob at N,
the
SB-20's
guide
number is
60(m) for full
output.
lf the
subject
is 15m
away, divide
60 by 15
to
get
f/4.
Unit:
m
(ft.)
LIght
output
Zoom
setting
ISO film
speed
1600
800 400 200 100 50
z3
Full
W
88
(zag)
62
(203)
44
\144)
31
loz)
22
\72)
15
(49)
11
(36)
N
120
(394)
85
Q7e)
60
(197)
+z
(138)
30
(e8)
21
(6e)
15
(49)
T
144
Qtzl
102
(335)
72
(236)
51
(167)
50
(1
1B)
25
G2)
18
(sg)
1t2
W
62
(203)
44
(qq)
JI
h02)
22
\72)
15
(49)
11
(36)
7.8
Q5)
N
85
Q7e)
60
(197)
42
(138)
30
(e8)
21
(oe)
15
(49)
11
(36)
T
102
(sgs)
72
(236)(167)
Jb
(1
18)
25
@2)
18
(5e)
13
(43)
1t4
W
44
\144)
JI
\102)
22
0z)
tc
(4e)
11
(36)
7.8
(2s)
5.5
(r8)
N
60
(rgz)
42
(138)
30
(eB)
21
(6s)
15
(49)
11
(36)
7.5
(2s)
T
IZ
(zso)
51
(167)
36
(1
18)
25
(82)
18
(sg)
13
(43)
q
(30)
1/8
W
QI
(102)
22
0z)
15
(4e)
11
(so)
7.8
{'25)
5.5
(18)
3.9
(13)
N
42
(138)
30
(e8)
21
(6s)
t3
(4e)
11
(36)
Qs)
A?
(7)
T
51
(roz)
36
(118)
25
(82)
18
(ss)
13
(43)
I
(30)
6.3
Qt)
1/16
W
22
/J2\
1q
(4e)
'II
(36)
7.8
Qsl
5.5
(18) (13)
2.7
8.8
N
30
(eB)
21
(6e)
'15
(49)
11
(36)
7.5
(25)
3.J
t17 )
3.7
'1l2)
T
Jb
(1
1B)
25
(82)
18
(5e)
13
(43)
(?n)
6.3
Qt)
(15)
32
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