Taking Photographs—Flash Photography94The D100 is equipped with a Guide Number 17/56 (ISO 200, m/ft; GuideNumber at ISO 100 is 12/39) Speedlight with a flash angle wide enough tocover 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 isinadequate, but to fill in shadows and backlit subjects or to add a catch lightto your subject’s eyes.Flash PhotographyUsing Built-in and Optional SpeedlightsFlash AngleWhile the built-in Speedlight can cover the field of view of a 20-mm lens, it may not beable to light the entire subject with some lenses or at some aperture settings.ISO AutoIf 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 SpeedlightIf an optional Speedlight is used with spot metering, Standard TTL flash for digital SLRwill be used. If the built-in Speedlight is raised when an optional Speedlight other thanthe SB-50DX is attached, the optional Speedlight will not fire. If an SB-50DX is set tomanual in the bounce flash position, both the built-in Speedlight and the SB-50DX willfire.
