Справочник Пользователя для Nikon D2HS

TTL fl ash control is available only with optional SB-series 800, 600, 80DX, 
28DX, and 50DX Speedlights.

SB-800, SB-600: i-TTL Flash Control
When the SB-800 or SB-600 is set to TTL, the camera automatically selects 
one of the following types of fl ash control:

i-TTL Balanced Fill-Flash for Digital SLR: Speedlight emits series of nearly invisible 
prefl ashes (monitor prefl ashes) immediately before main fl ash.  Prefl ashes refl ected 
from objects in all areas of frame are picked up by fi ve-segment TTL fl ash control 
sensor or 1,005-pixel RGB sensor and are analyzed in combination with information 
from matrix metering system to adjust fl ash 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 fl ash output.  Precision of calculation can 
be increased for non-CPU lenses by providing lens data (focal length and maximum 
aperture; 

 121–124).  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.  Recom-
mended for shots in which main subject is emphasized at expense of background 
details, or when exposure compensation is used.  Standard i-TTL fl ash for digital SLR 
is activated automatically when spot metering is selected.