Nikon D810 User Manual page 218

A
Flash Control Mode
The camera supports the following i-TTL flash control modes:
• i-TTL balanced fill-flash for digital SLR: Flash emits series of nearly invisible
preflashes (monitor preflashes) immediately before main flash.
Preflashes reflected from objects in all areas of frame are picked up by
RGB sensor with approximately 91K (91,000) pixels and are analyzed
in combination with range information from matrix metering system
to adjust flash output for natural balance between main subject and
ambient background lighting. If type G, E, or D lens is used, distance
information is included when calculating flash output. Precision of
calculation can be increased for non-CPU lenses by providing lens
data (focal length and maximum aperture; see 0 229). Not available
when spot metering is used.
• Standard i-TTL flash for digital SLR: Flash output adjusted to bring lighting
in frame to standard level; brightness of background is not taken into
account. Recommended for shots in which main subject is
emphasized at expense of background details, or when exposure
compensation is used. Standard i-TTL flash for digital SLR is activated
automatically when spot metering is selected.
The flash control mode for the built-in flash can be selected using
Custom Setting e3 (Flash cntrl for built-in flash, 0 331). The
information display shows the flash control mode for the built-in flash
as follows:
i-TTL
Manual
Repeating flash
Commander mode
194
Flash sync Auto FP (0 329, 330)
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