Flash Power Calculator
Enter your flash Guide Number (in feet or meters at ISO 100) from the manual, then adjust ISO and aperture to see optimal distances for each power level. Click on a row to see +/- 0.3 0.7 EV calculations.
ft
m
ISO
400
Aperture
f/5.6
Guide No. (ISO100)
141.1 ft
Suggested Shutter (+0EV)
1/4
Actual Shutter
1/4
Flash Power to Distance Chart