V1.02
Thom Hogan’s Complete Guide to the Nikon D300
Page 600
used with extremely wide lenses, thus AF Assist is
automatically turned off by the camera when focal lengths
wider than 16mm are used.
Flash Modes
Like most Nikon 35mm film camera bodies, the actual
method used to calculate flash exposure varies considerably
depending upon camera settings, flash settings, and the lens
being used. A full discussion of the intricacies of Nikon’s flash
system can be found in my
Nikon Digital Flash Guide
, but
what follows is a simple recap of what’s available using a
D300.
i-TTL Balanced Fill-Flash
(
TTL BL
on external flash LCD; no indicator for internal
flash): this is the
default
flash mode for most camera settings.
Requires use of a D, G, P, AF, AF-I, or AF-S lens (basically any
lens that has what Nikon calls a CPU in it
144
). The camera
balances exposure information from the matrix meter with
additional information from the lens (focal length, aperture,
and distance at which the lens is focused) and from a series of
nearly invisible pre-flashes, which the metering CCD in the
D300’s viewfinder analyzes. When set in this mode, the D300
normally attempts to balance the flash with the ambient light.
Generally, less flash is produced in this mode than if you set
the flash manually for the flash-to-subject distance.
Note that
no
measurement of the light produced by the flash
is made by the D300
during
the exposure, as is done on the
35mm film camera bodies; the amount of flash produced is
completely determined at the end of the pre-flash
measurements, which occur before the shutter opens. Thus, if
lighting conditions change rapidly, the amount of flash
produced may be incorrect. That happens rarely, but the
lower power of the preflash does make the accuracy of the
144
On a D300, AI and AI-S lenses can also support balanced TTL
if
you’ve entered
their data using
Non-CPU lens data
(on the SHOOTING menu).
