User manual

ISO sensitivity factors

For sensitivities other than ISO 100, multiply the guide number by the factors shown in the

table below.

To calculate the correct aperture

Calculate the correct aperture by using this equation and the guide number table,

according to the ISO sensitivity, shooting distance, flash output level and zoom-head

position that are set:

f/stop (aperture) = Guide number (GN at ISO 100; m/ft.) x ISO sensitivity

factor ÷ Shooting distance (m/ft)

For example, for the ISO sensitivity of 400 (or ISO sensitivity factor: 2), with the zoom-head

position adjusted to 28mm, and the flash output level set to M1/1:

• Referring to the guide number table, determine the guide number as 32/105 (m/ft.).

When the shooting distance is 4m (13.1 ft.), the correct aperture value is:

32/105 (GN at ISO 100, m/ft) x 2 (ISO sensitivity factor for ISO 400) ÷ 4/13.1

(shooting distance; m/ft.) = 16 (aperture)

• Set the aperture value 16 on both the SB-800 and the camera or lens.

To obtain the correct flash output level

Calculate the guide number (GN at ISO 100; m/ft.) by using this equation, according to the

shooting distance and aperture required.

Guide number (GN at ISO 100; m/ft.) = Shooting distance (m/ft) x Aperture (f/) ÷ 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 SB-800.

For example, for the ISO sensitivity of 400 (or ISO sensitivity factor: 2) and the shooting

distance of 4m (13.1 ft) with an aperture of f/8:

4/13.1 (shooting distance; m/ft.) x 8 (aperture value) ÷ 2 (ISO sensitivity factor of

ISO 400) = 16/52 (GN at ISO 100; m/ft.)

• When the zoom-head position is adjusted to 28mm, set M1/4 flash output level on the

SB-800, which can be obtained from GN 16/52 (m/ft.) corresponding to the zoom-head

position of 28mm referring to the guide number table.

• In Distance-priority manual flash operation, the correct flash output level is automatically

determined by the SB-800 according to the shooting distance, aperture and ISO

sensitivity that are set.

To calculate the shooting distance

Calculate the shooting distance (m/ft.) by using this equation and the guide number table,

according to the ISO sensitivity, aperture value, flash output level and zoom-head position

that are set:

Shooting distance (m/ft.) = Guide number (GN at ISO 100; m/ft.) x ISO sensitivity

factor ÷ Aperture (f/)

Detailed operation

ISO 25 50 100 200 400 800 1600

Factors x0.5 x0.71 x1 x1.4 x2 x2.8 x4