Nikon D700 - Manual (Page 134)

108
S
Auto ISO Sensitivity Control
If Off (the default setting) is chosen for the ISO sensitivity auto
control option in the shooting menu, ISO sensitivity will remain
fixed at the value selected by the user (see page 106). If On is
chosen, ISO sensitivity will automatically be adjusted if optimal
exposure can not be achieved at the value selected by the user
(flash level is adjusted appropriately). The maximum value for
auto ISO sensitivity can be selected using the Maximum
sensitivity option in the ISO sensitivity auto control menu (the
minimum value for auto ISO sensitivity is automatically set to ISO
200). In exposure modes P and A, sensitivity will only be adjusted if
underexposure would result at the shutter speed selected for
Minimum shutter speed. Slower shutter speeds may be used if
optimum exposure can not be achieved at the ISO sensitivity value
selected for Maximum sensitivity.
When On is selected, the control panel and
viewfinder show ISO-AUTO. When sensitivity
is altered from the value selected by the
user, these indicators blink and the altered
value is shown in the viewfinder.