Flash Guide Number (at ISO 100)
Zoom Head Position
Factor: 0.90×
Settings
High-Speed Sync (HSS)
Aperture
Results
Effective GN
52
at ISO 100, 1/1 (Full)Max Distance
9.3 m
at f/5.6Quick Reference at GN 52
| Aperture | Max Distance |
|---|---|
| f/1.4 | 37.3 m |
| f/2 | 26.1 m |
| f/2.8 | 18.6 m |
| f/4 | 13.1 m |
| f/5.6 | 9.3 m |
| f/8 | 6.5 m |
| f/11 | 4.7 m |
| f/16 | 3.3 m |
| f/22 | 2.4 m |
Guide Number Formula
- GN = Distance × Aperture
- Distance = GN ÷ Aperture
- Aperture = GN ÷ Distance
- ISO adjustment: GN doubles when ISO quadruples (×2 per 2 stops)
- Power adjustment: Halving power reduces GN by √2 (≈0.7×)
- Zoom head: Narrower beam = more reach, wider beam = less reach