Ai-TTL Flash Control
In i-TTL flash control, the camera adjusts the flash level based on reflections from a series of nearly invisible pre-flashes (monitor pre- flashes) emitted by the flash unit immediately before firing. There are two types of i-TTL flash control: i-TTL balanced fill-flash, in which flash output is adjusted for a natural balance between the main subject and ambient background lighting, and standard i-TTL flash, in which flash output is adjusted to bright lighting in the frame to a standard level without taking the brightness of the background into account. To use i-TTL flash control with optional flash units other than the SB-400, select i-TTL flash control mode on the flash unit before shooting. When using an SB-700 or SB-400, note that i-TTL balanced fill-flash is activated automatically when matrix or center-weighted metering is selected with the camera, while standard i-TTL is used with spot metering.
AOptional Flash Units
Optional flash units enter standby when the camera is turned off; check the flash-ready indicator on the flash unit before shooting. Auto power zoom is supported with SB-910, SB-900, SB-800, SB-700, and SB-600 flash units, but note that a wide panel may be required to eliminate vignetting at ranges under 2 m (6 ft 7 in.). Advanced Wireless Lighting, auto FP high-speed sync, and AF-assist for multi-area AF are not supported.
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