V1.02
Thom Hogan’s Complete Guide to the Nikon D300
Page 603
In other words, the camera does not attempt to balance
background exposure with subject exposure, as it does in the
Balanced Fill-Flash TTL mode.
High-Speed TTL (TTL FP)
(
TTL BL FP
or
TTL FP
on external flash LCD; only available
on SB-600, SB-800 and RB-200 Speedlights): The D300
supports a variant for both Balanced Fill-Flash TTL and
Standard TTL: FP. FP doesn’t change the type of TTL being
performed (Standard or Balanced), it only changes the
allowable shutter speeds. If FP is active—and you make it so
by setting Custom Setting #E1 to
1/250 (FP auto)
or
1/320
(FP auto)
—the upper shutter speed limit of 1/250 for flash is
removed. That may seem like something you’d want to have
available all the time (it is a setting I suggest as a default), but
be careful. Shutter speeds above 1/250 cause the flash to
produce its light differently. Instead of a single flash burst, the
output is done in a series of very short, small bursts of flash,
which reduces the overall output of the flash by a bit over two
stops. If you use the TTL FP option, make sure to pay attention
to the range display on the external flash LCD whenever you
shoot at faster than 1/250; the flash may not be able to cover
the distance you’re shooting at. For internal flash, consult the
range table later in this eBook.