Nikon D100 - Manual (Page 106)

Taking Photographs—Flash Photography
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The D100 is equipped with a Guide Number 17/56 (ISO 200, m/ft; Guide
Number at ISO 100 is 12/39) Speedlight with a flash angle wide enough to
cover the field of view of a 20-mm lens. With a CPU lens, the built-in Speed-
light supports D-TTL flash control for flash photographs with a natural bal-
ance. The built-in Speedlight can be used not only when natural lighting is
inadequate, but to fill in shadows and backlit subjects or to add a catch light
to your subject’s eyes.
Flash Photography
Using Built-in and Optional Speedlights
Flash Angle
While the built-in Speedlight can cover the field of view of a 20-mm lens, it may not be
able to light the entire subject with some lenses or at some aperture settings.
ISO Auto
If a Speedlight is used when Custom Setting 3 (ISO Auto) is on, sensitivity (ISO equiva-
lency) will be fixed at the value selected by the user.
Using an Optional Speedlight
If an optional Speedlight is used with spot metering, Standard TTL flash for digital SLR
will be used. If the built-in Speedlight is raised when an optional Speedlight other than
the SB-50DX is attached, the optional Speedlight will not fire. If an SB-50DX is set to
manual in the bounce flash position, both the built-in Speedlight and the SB-50DX will
fire.