Flash shooting in the 1/300 TTL
Use the guide number table and equation to calculate the farthest flash shooting distance, according to each
D (farthest flash shooting distance)
= Guide number ÷ f/stop (aperture)
Guide number (m/ft.) in the 1/300 TTL
ISO |
|
|
|
| |||
sensitivity | 14* | 24 | 28 | 35 | 50 | 70 | 85 |
25 | 2.9/9.5 | 4.7/15 | 5.1/17 | 5.6/18 | 6.6/22 | 7.3/24 | 8/26 |
50 | 4.0/13 | 6.7/22 | 7.2/24 | 8/26 | 9.3/31 | 10.3/34 | 11.4/37 |
100 | 5.7/19 | 9.4/31 | 10.1/33 | 11.3/37 | 13.1/43 | 14.5/48 | 16/52 |
200 | 8/26 | 13.2/43 | 14.1/46 | 15.8/52 | 18.3/60 | 20/66 | 22.4/73 |
400 | 11.4/37 | 18.8/62 | 20.2/66 | 22.6/74 | 26.2/86 | 29/95 | 32/105 |
800 | 16/52 | 26.3/86 | 28.3/93 | 31.6/104 | 36.7/120 | 40.6/133 | 44.8/147 |
*With the
•For example, when shooting with an ISO sensitivity of 100, at a 35mm
D = 11.3 ÷ 5.6 (f/stop) = 2.0 (in meters) (farthest flash shooting distance)
D = 37 ÷ 5.6 (f/stop) = 6.6 (in feet) (farthest flash shooting distance)
76