Nikon D800 User Manual (en)

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 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 
0 212). 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
0 301). The 
information display shows the flash control mode for the built-in flash as 
Flash sync
Auto FP (
Repeating flash
Commander mode