Nikon SB-80DX - Manual (Page 88)

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Adjusting the flash output level in M (manual) mode
Adjusting the slave flash unit’s flash output level manually
m Use the following equation to determine the proper manual flash output level
of the slave flash unit, depending on your creative preferences.
GN = F x D
where GN is the guide number of the slave flash unit (in meters/feet), F is the
lens aperture in use, and D is the distance between the slave flash unit and
the subject (in meters/feet).
For example, when using an ISO sensitivity of 100 and shooting a subject at a
distance of 2m (6.6 ft.) with the SB-80DX’s zoom-head position adjusted to
28mm, and a lens aperture of f/4,
GN = 4 x 2 = 8 (in meters)
GN = 4 x 6.6 = approx. 26 (in feet)
Therefore, to get the correct exposure, refer to the Guide Number table (p. 45)
and adjust the flash output level to M1/16.
nRefer to “Determining the aperture and flash output level in the Manual mode” (p. 44).
Adjusting the slave flash unit’s flash output level in the Non-TTL auto
flash (A) mode
m Determine the flash output level by setting the aperture on the slave flash unit
and camera.
1 Set the same ISO sensitivity on the slave flash unit as set on your camera.
2 Set the same aperture on both the lens and the slave flash unit to obtain the
correct exposure.
nDepending on your creative preferences, you can intentionally overexpose or
underexpose the picture by modifying the aperture.
nThe above setting is applicable only when both the master and slave flash units are
pointed in the same directions. Not applicable, if the directions differ.
nRefer to “Setting apertures in the non-TTL auto flash mode” (p. 41) for more details.
Wireless multiple flash shooting