Pentax IST DS Digital Camera User Manual


 
150
5
Function Reference
The following equation calculates the aperture value for shooting
distances.
Aperture Value Used F = Guide number ÷ shooting distance
When sensitivity is [ISO200] and shooting distance is 5.2 m, aperture
value is:
F = 15.6 ÷ 5.2 = 3
If the resulting number (3, in the above example) is not available as a
lens aperture, the smaller number that is closest (2.8, in the above
example) is generally used.
Calculating Aperture Value from Shooting Distance