Pentax AF-360FGZ manual Calculating the Flash Effective Range, Example

00_AF360FGZ.book Page 77 Tuesday, June 13, 2006 12:09 PM

Flash Effective Range

nCalculating the Flash Effective

Range

When setting the lens to manual f/stop, calculate the guide number at full flash with the use of flash's zoom position and ISO. Divide the resulting guide number by the aperture in use. Thus, the maximum distance is obtained. The minimum distance is obtained in dividing this max. distance by approx. 10.

However, if the minimum distance obtained is 0.7m or less, the minimum distance will be 0.7m. Refer to page 82 for the guide number table.

Example:

With a 50 mm lens at f/4 and sensitivity at ISO100

For the zoom position 50mm and sensitivity at ISO100, the guide number is 30.  30 (guide number) /4 (aperture) = 7.5m (max. distance)

 7.5m (max. distance) /10 = 0.75m (min. distance) Thus, flash effective range is approx. 0.75m - 7.5m.

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