Nikon D500 User Manual page 168

A
Metered Area
In spot metering, exposure will be locked at the value metered at the
selected focus point (0 128). In center-weighted metering, exposure
will be locked at the value metered in an 8-mm circle in the center of
the viewfinder.
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Adjusting Shutter Speed and Aperture
While exposure lock is in effect, the following settings can be adjusted
without altering the metered value for exposure:
Exposure mode
P
S
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The new values can be confirmed in the viewfinder and control panel.
Note that the metering method can not be changed while exposure
lock is in effect.
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See Also
If On (half press) is selected for Custom Setting c1 (Shutter-release
button AE-L, 0 296), exposure will lock when the shutter-release
button is pressed halfway.
142
Shutter speed and aperture (flexible program; 0 132)
Setting
Shutter speed
Aperture