Nikon Z8 User Manual page 214

Tip: The Photo Shooting Menu [ISO Sensitivity Settings] Option
ISO sensitivity can also be adjusted using the [ISO sensitivity
settings] item in the photo shooting menu.
Tip: Hi 0.3–Hi 2.0
A setting of [Hi 0.3] corresponds to an ISO sensitivity approximately 0.3 EV higher than ISO 25600
(ISO 32000 equivalent) and [Hi 2.0] to an ISO sensitivity approximately 2 EV higher (ISO 102400
equivalent). Note that pictures taken at these settings are particularly prone to "noise" in the form of
randomly-spaced bright pixels, fog, or lines.
Tip: Lo 0.3–Lo 1.0
[Lo 0.3] corresponds to an ISO sensitivity about 0.3 EV below ISO 64 (ISO 50 equivalent). [Lo 1.0] is
roughly 1 EV below ISO 64 (ISO 32 equivalent). Use for larger apertures or slower shutter speeds when
lighting is bright. Highlights may be overexposed. In most cases, ISO sensitivities of ISO [64] or above
are recommended.
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ISO Sensitivity