A12: Built-In Af-Assist Illuminator - Nikon Z 8 Reference Manual

a12: Built-in AF-Assist Illuminator

Choose whether the built-in AF-assist illuminator lights to assist the focus operation in photo mode
when lighting is poor.
Option
In photo mode, the illuminator will light as required when AF‑S is selected for focus
[ON]
mode.
The illuminator does not light to assist the focus operation. The camera may not be able
[OFF]
to focus when lighting is poor.
D
The AF-Assist Illuminator
The AF-assist illuminator has a range of about 1–3 m (3 ft 4 in.–9 ft 10 in.).
Remove lens hoods when using the illuminator.
Do not obstruct the AF-assist illuminator while it is lit.
Some lenses may block the light from the AF-assist illuminator at some or all focus distances.
Information on these restrictions is available from the Nikon Download Center.
https://downloadcenter.nikonimglib.com/
G button U A Custom Settings menu
Description
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a12: Built-in AF-Assist Illuminator