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Flash Exposure Calculator
Work out flash exposure using guide number, ISO, aperture, and subject distance.
Results
- Guide number at your ISO
- 40.0 m
- Required aperture at subject distance
- f/8.0
- Max flash distance at your aperture
- 5.0 m
Your flash's effective guide number once your chosen ISO is factored in.
The aperture that gives correct flash exposure at the subject distance you entered.
The farthest a subject can be from the flash and still be correctly exposed at this aperture.