Nikon D780 Reference Manual page 131

A
Locking Focus When AF-S Is Selected for AF Mode
Focus will lock while the shutter-release button is pressed halfway. Focus
will also lock while the A button is pressed.
A
Using the Shutter-Release Button for Exposure Lock
If [On (half press)] is selected for Custom Setting c1 [Shutter-release
button AE-L], exposure will lock while the shutter-release button is
pressed halfway.
A
Taking Multiple Shots at the Same Focus Distance
•
Focus will remain locked if you keep the A button pressed between
shots, allowing several photographs in succession to be taken at the
same focus setting.
•
Focus will also remain locked if you keep the shutter-release button
pressed halfway between shots.
Camera Controls
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