Nikon D500 User Manual

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198
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i-TTL Flash Control
When a CLS-compatible flash unit is set to TTL, the camera 
automatically selects one of the following types of flash control:
• i-TTL balanced fill-flash for digital SLR: Flash unit 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 180K (180,000) 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 
page 250). Not available when spot metering is used.
• Standard i-TTL fill-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 fill-flash for digital SLR is 
activated automatically when spot metering is selected.