Nikon D800 - Manual (Page 135)

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S
Auto ISO Sensitivity Control
If On is selected for ISO sensitivity settings > Auto ISO
sensitivity control in the shooting menu, ISO sensitivity will
automatically be adjusted if optimal exposure can not be achieved
at the value selected by the user (ISO sensitivity is adjusted
appropriately when the flash is used).
1
Select Auto ISO
sensitivity control for
ISO sensitivity settings
in the shooting menu.
To display the menus, press
the
G button. Select ISO
sensitivity settings in the shooting menu, highlight Auto ISO
sensitivity control, and press
2.
2
Select On.
Highlight On and press J
(if Off is selected, ISO
sensitivity will remain fixed
at the value selected by the
user).
A
Auto ISO Sensitivity Control
Noise (randomly-spaced bright pixels, fog, or lines) is more likely at
higher sensitivities. Use the High ISO NR option in the shooting menu
to reduce noise (see page 277). When a flash is used, the value selected
for Minimum shutter speed is ignored in favor of the option selected
for Custom Setting e1 (Flash sync speed,
0 299). Note that ISO
sensitivity may be raised automatically when auto ISO sensitivity
control is used in combination with slow sync flash modes (available
with the built-in flash and the optional flash units listed on page 381),
possibly preventing the camera from selecting slow shutter speeds.
G button
J button