Nikon D300S User Manual page 206

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Using FV Lock with Optional Flash Units
FV lock is also available with SB-900, SB-800, SB-600, SB-400, and
SB-R200 flash units (available separately). Set the optional flash to TTL
mode (the SB-900 and SB-800 can also be used in AA mode; see the
flash manual for details). While FV lock is in effect, flash output will
automatically be adjusted for changes in flash zoom head position.
When Commander mode is selected for Custom Setting e3 (Flash cntrl
for built-in flash, 0 283), FV lock can be used with remote SB-900,
SB-800, SB-600, or SB-R200 flash units if (a) any of the built-in flash, flash
group A, or flash group B is in TTL mode, or (b) a flash group is
composed entirely of SB-900 and SB-800 flash units in TTL or AA mode.
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Metering
The metering areas for FV lock when using optional flash unit are as
follows:
Flash unit
Stand-alone flash unit
Used with other flash
units (Advanced
Wireless Lighting)
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See Also
For information on using the depth-of-field preview or AE-L/AF-L button
for FV lock, see Custom Setting f6 (Assign preview button, 0 296) or
Custom Setting f7 (Assign AE-L/AF-L button, 0 296).
l
180
Flash mode
i-TTL
AA Area metered by flash exposure meter
i-TTL
AA
Area metered by flash exposure meter
A (master flash)
Metered area
4-mm circle in center of frame
Entire frame