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Manual Flash Planner
Flash
Guide Number Calculator
Master manual flash exposure in any situation.
Flash & Camera Settings
Guide Number (at ISO 100, full power)
GN 40
Flash Power
1/1 — Full
1/2 — Half
1/4
1/8
1/16
1/32
1/64
ISO
100
200
400
800
1600
3200
Subject Distance
3.0 m
m
ft
Your Aperture
f / 1.2
f / 1.4
f / 1.8
f / 2
f / 2.8
f / 4
f / 5.6
f / 8
f / 11
f / 16
f / 22
Flash Reach — Optimal distance zone for your settings
—
Effective GN
—
Aperture Needed
—
Max Distance
—
Exposure Delta
—
Calculations use GN = Distance × Aperture (ISO 100 baseline). Power fractions reduce GN by √(fraction).