●●● Determining the aperture and flash output level in the
Manual mode
In the Manual mode, use the guide number table and the following equation to calculate the aperture, flash output level and shooting distance to obtain the correct exposure.
•The guide number (GN at ISO 100; m/ft) indicates the amount of light generated by the flash. The larger the number, the greater the flash output.
Guide number (ISO 100, m/ft)
Flash output |
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level | 14* | 24 | 28 | 35 | 50 | 70 | 85 |
M1/1 | 14.0/45.9 | 26.0/85.3 | 28.0/91.9 | 30.0/98.4 | 36.0/118.1 | 38.0/124.7 | 40.0/131.2 |
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M1/2 | 9.9/32.5 | 18.4/60.4 | 19.8/65.0 | 21.2/69.6 | 25.5/83.7 | 26.9/88.3 | 28.3/92.8 |
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M1/4 | 7.0/23.0 | 13.0/42.7 | 14.0/45.9 | 15.0/49.2 | 18.0/59.1 | 19.0/62.3 | 20.0/65.6 |
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M1/8 | 4.9/16.1 | 9.2/30.2 | 9.9/32.5 | 10.6/34.8 | 12.7/41.7 | 13.4/44.0 | 14.1/46.3 |
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M1/16 | 3.5/11.5 | 6.5/21.3 | 7.0/23.0 | 7.5/24.6 | 9.0/29.5 | 9.5/31.2 | 10.0/32.8 |
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M1/32 | 2.5/8.2 | 4.6/15.1 | 4.9/16.1 | 5.3/17.4 | 6.4/21.0 | 6.7/22.0 | 7.1/23.3 |
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M1/64 | 1.8/5.9 | 3.3/10.8 | 3.5/11.5 | 3.8/12.5 | 4.5/14.8 | 4.8/15.7 | 5.0/16.4 |
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*With the
To calculate the correct aperture
Calculate the correct aperture by using this equation and the guide number table, according to the flash output level,
f/stop (aperture) = guide number (GN) x ISO sensitivity factor ÷ Shooting distance (m/ft)
• Set this aperture on the camera or lens.
To calculate the guide number
Calculate the guide number by using this equation, according to the shooting distance and aperture required.
Guide number (GN) = Shooting distance (m/ft) x Aperture ÷ ISO sensitivity factor
•Referring to the guide number table, determine an appropriate flash output level corresponding to the guide number obtained above, then set the same value on the
ISO sensitivity factors
For sensitivities other than ISO 100, multiply the guide number by the factors shown in the table below.
ISO | 25 | 50 | 100 | 200 | 400 | 800 | 1600 |
Factors | x0.5 | x0.71 | x1 | x1.4 | x2 | x2.8 | x4 |
Detailed operation
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