Nikon SB-28 - Manual (Page 30)

Flash shooting distance range in 1/300 TTL High-Speed
Flash sync operation (F5 only)
In combination with the F5 camera, 1/300 High-Speed Flash Sync (with
Custom Setting; 1/250 sec. at normal setting) is possible. But the farthest
flash shooting distance cannot be read from the indicator bars
_ on the
SB-28 in TTL Auto Flash
t
Mode.
In this case, use the guide number table and equation for calculating this
distance according to each zoom-head position.
Guide number
D (farthest flash shooting distance) = ——————————
f/stop (aperture)
For example, when shooting with ISO 100 film, at a 35mm zoom-head position and
an aperture of f/5.6:
D = 14/5.6 = 2.5 (measured in meters)
D = 46/5.6 = 8.2 (measured in feet)
The farthest flash shooting distance is 2.5m (8.2ft). You can read the closest
shooting distance from the SB-28’s indicator bars
_.
• For film speeds other than ISO 100, multiply the figures in the table above by the
factors shown below.
30
TTL Auto Flash
t Mode
Guide number (at ISO 100 for m/ft)
Zoom head position
Guide number
18mm 20mm 24mm 28mm 35mm 50mm 70mm 85mm
8/26 8/26 11/36 12/39 14/46 16/53 18/59 19/62
ISO film speed
Factor
25 50 200 400 800
x 0.5 x 0.71 x 1.4 x 2 x 2.8
For cameras in Group I: F5 only