Nikon SB-80DX - Manual (Page 45)

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Detailed operation
ISO 25 50 100 200 400 800 1600
Factors x0.5 x0.71 x1 x1.4 x2 x2.8 x4
To calculate the correct aperture
n Calculate the correct aperture by using this equation and the guide number
table, according to the ISO sensitivity and flash output level that are set:
f/stop (aperture) = Guide number (GN) x ISO sensitivity factor ÷ Shooting distance (m/ft)
n Set the same aperture on both the SB-80DX and the camera or lens.
To calculate the guide number
n 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 x ISO sensitivity factor
n 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 SB-80DX.
ISO sensitivity factors
n For sensitivity other than ISO 100, multiply the guide number at an ISO
sensitivity of 100 by the factors shown in the guide number table.
* 1 With the Diffusion Dome attached and the built-in wide-flash adapter in place
* 2 With the Diffusion Dome attached
* 3 With the built-in wide-flash adapter in place
Zoom-head position (mm)
∗
1
∗
2 14
∗
3 17
∗
3 24 28 35 50 70 85 105
M1/1 12.5/41 16/52 17/56 19/62 32/105 34/112 38/125 44/144 50/164 53/174 56/184
M1/2 8.8/29 11.3/37 12/39 13.4/44 22.6/74 24/79 26.8/88 31/102 35/115 37.5/123 40/131
M1/4 6.3/21 8.0/26 8.5/28 9.5/31 16/52 17/56 19/62 22/72 25/82 26.5/87 28/92
M1/8 4.4/14 5.6/18 6.0/20 6.7/22 11.3/37 12/39 13.4/44 15.5/51 17.7/58 18.7/61 19.8/65
M1/16 3.1/10 4.0/13 4.3/14 4.8/16 8.0/26 8.5/28 9.5/31 11/36 12.5/41 13.3/44 14/46
M1/32 2.2/7 2.8/9 3.0/10 3.4/11 5.6/18 6.0/20 6.7/22 7.8/26 8.8/29 9.4/31 9.9/32
M1/64 1.6/5 2.0/7 2.1/7 2.4/8 4.0/13 4.3/14 4.8/16 5.5/18 6.3/21 6.6/22 7.0/23
M1/128 1.1/4 1.4/5 1.5/5 1.7/6 2.8/9 3.0/10 3.4/11 3.9/13 4.4/14 4.7/15 4.9/16
FP - - - - 10.7 /35 11.3/37 12.7/42 14.7/48 16.7/55 17.7/58 18.7/61
Guide number (ISO 100, m/ft)
Flash
output
level