Filter
Top Products
11-18
With ISO set to 200, you can locate the guide number in the table (shown on the previous
page), then use the formulas on the previous page to determine aperture or the optimal
flash shooting distance.
For example, with ISO 200, a Flash output level of 1/1 (full), a Zoom-head position of
35 mm, the guide number is 51/167. If the Flash shooting distance is 9 meters
(approximately 30 feet), the appropriate aperture is:
f/stop = 51/9 (meters) = 5.67 = approximately 5.6
f/stop = 167/30 (feet) = 5.57 = approximately 5.6
For ISO settings other than 200, multiply the guide number by the factors shown below:
For example, if the ISO in the previous example was 800 (rather than 200), the guide
number is 102 (51 x 2).
ISO Setting Multiplier
80 0.632
200 1
400 1.414
800 2
1600 2.827