Guide numbers for determining the correct aperture, Calculating the correct aperture, Calculating the shooting distance – Kodak DCS 700 User Manual
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Guide Numbers for Determining the Correct Aperture
Guide numbers help you determine a correct exposure or proper aperture (f/stop) when
using the SB-28D Speedlight in the Manual
or Repeating Flash
mode.
The guide number represents the amount of light at ISO 200 for meters/feet (m/ft)
generated by the flash. With the SB-28D Speedlight, you can calculate a correct aperture
or desired flash shooting distance by using the following equations and the guide number
table.
Calculating the Correct Aperture
Calculating the Shooting Distance
Guide Number Table
Guide Numbers in meters/feet at ISO 200 in Manual and Repeating Flash modes.
Flash
Output
Level
Zoom-head position
18 mm
20 mm
24 mm
28 mm
35 mm
50 mm
70 mm
85 mm
1/1 (full)
25/84
28/93
42/139
45/148
51/167
59/195
68/223
71/232
1/2
18/59
20/66
30/98
32/105
36/118
42/138
48/157
50/164
1/4
12.7/42
14/46
21/69
22.5/74
25.5/84
30/98
34/112
36/118
1/8
9/30
10/33
15/49
16/53
18/59
21/69
24/79
25/82
1/16
6.4/21
7/23
10.5/35
11.3/37
12.7/42
15/49
17/56
18/59
1/32
4.5/15
5/16
7.5/25
8/26
9/30
10.5/35
12/39
12.7/42
1/64
3.2/10
3.5/11
5.3/17
5.7/19
6.4/21
7.5/25
8.5/28
9/30
M
f/stop (aperture) =
Guide number
Flash shooting distance (m/ft)
flash shooting distance (m/ft) =
Guide number
f/stop (aperture)