Nikon D5500 - Manual (Page 274)

250 A Custom Settings: Fine-Tuning Camera Settings
Choose whether the built-in AF-assist
illuminator lights to assist the focus
operation when lighting is poor.
Choose On to use the exposure indicator to determine whether
the camera is correctly focused in manual focus mode (
0 88;
note that this function is not available in shooting mode M, when
the exposure indicator instead shows whether the subject is
correctly exposed).
a3: Built-in AF-assist Illuminator
G button
➜ A Custom Settings menu
Option Description
On
The AF-assist illuminator lights when lighting is poor (for
more information, see page 352).
Off
The AF-assist illuminator does not light to assist the focus
operation. The camera may not be able to focus using
autofocus when lighting is poor.
a4: Rangefinder
G button
➜ A Custom Settings menu
Indicator Description
Subject in focus.
Focus point is slightly in front of subject.
AF-assist illuminator