Nikon Z8 User Manual page 216

D
Cautions: Auto ISO Sensitivity Control
If the value currently selected for [ISO sensitivity] is higher than that chosen for [Maximum
sensitivity], the value chosen for [ISO sensitivity] will serve as the upper limit for auto ISO
sensitivity control.
During flash photography, shutter speed is limited to the range defined by the values selected for
Custom Settings e1 [Flash sync speed] and e2 [Flash shutter speed]. If the value selected for
[Minimum shutter speed] is not in this range, the value selected for Custom Setting e2 [Flash
shutter speed] becomes the effective minimum shutter speed.
Except in mode M, videos are recorded using auto ISO sensitivity control. Auto ISO sensitivity
control can be enabled for video recording in mode M by selecting [ON] for [ISO sensitivity
settings] > [Auto ISO control (mode M)] in the video recording menu.
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ISO Sensitivity