C: timers/ae lock, C1: shutter-release button ae-l, C2: standby timer – Nikon D810 User Manual
Page 343: C3: self-timer, 0 319) f, 0 319); the int

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If On is selected, exposure will lock when the shutter-release
button is pressed halfway.
Choose how long the camera continues to meter exposure
when no operations are performed. The shutter-speed and
aperture displays in the control panel and viewfinder turn off
automatically when the standby timer expires.
Choose a shorter standby timer delay for longer battery life.
Choose the length of the shutter release delay, the number of
shots taken, and the interval between shots in self-timer mode
(0 106).
• Self-timer delay: Choose the length of the shutter-release delay.
• Number of shots: Press 1 and 3 to choose the number of shots
taken each time the shutter-release button is pressed.
• Interval between shots: Choose the interval between shots when
the Number of shots is more than 1.
c: Timers/AE Lock
c1: Shutter-Release Button AE-L
G
button ➜ A Custom Settings menu
c2: Standby Timer
G
button ➜ A Custom Settings menu
c3: Self-Timer
G
button ➜ A Custom Settings menu