Nikon D100 Manual page 119

Using Built-in and Optional Speedlights
Notes on Optional Speedlights (Continued)
If an optional Speedlight with red-eye reduction is attached when the camera flash sync
mode is set to red-eye reduction or auto with red-eye reduction, the red-eye reduction
lamp on the optional Speedlight will be used.
On Speedlights with a built-in AF assist illuminator (SB-series 80DX, 28DX, 28, 27, and
26), the AF-assist illuminator will only light if all of the following conditions are met:
focus mode is set to single-servo auto, an AF-Nikkor lens is used, the subject is poorly
lit, and the center focus area is selected or dynamic-area AF is used in combination with
closest-subject priority. When the SB-24 is used with the SK-6 power bracket, neither
the AF-assist illuminator on the Speedlight nor the camera AF-assist illuminator will
light.
In auto multi program, the maximum aperture (minimum f/-number) is limited accord-
ing to sensitivity (ISO equivalency), as shown below:
Maximum aperture at an ISO equivalent of
200 250 320 400 500 640 800 1000 1250 1600
4.8 5 5.3 5.6 6 6.3 6.7 7.1 7.6 8
For each one-step increase in sensitivity (e.g., from 200 to 400), aperture is stopped
down by half an f/-stop. If the maximum aperture of the lens is smaller than given
above, the maximum value for aperture will be the maximum aperture of the lens.
Use the AS-15 accessory shoe adapter (available separately) when attaching flash ac-
cessories via a sync cable.
If flash compensation is performed with an optional Speedlight, the flash compensa-
tion indicator will appear in the viewfinder, but the amount of flash compensation will
not be displayed.
When an SC-17 sync cable is used for off-camera flash photography, correct exposure
may not be achieved in D-TTL mode. We recommend that you choose spot metering to
select Standard TTL Flash for Digital SLR. Take a test shot and view the results in the
monitor.
TTL flash control can not be used for multi-flash photography.
In D-TTL mode, use the flash panel provided with your Speedlight. Do not use other
panels such as diffusion panels, as this may produce incorrect exposure.
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