C: Timers/Ae Lock; C1: Shutter-Release Button Ae-L; C2: Auto Meter-Off Delay; C3: Self-Timer - Nikon D90 User Manual

c: Timers/AE Lock

c1: Shutter-Release Button AE-L

At the default setting of Off, exposure only locks when the AE-L/AF-L button is pressed.
If On is selected, exposure will also lock when the shutter-release button is pressed
halfway. This option is available in all shooting modes.

c2: Auto Meter-off Delay

This option (available in all shooting modes) controls how long
the camera continues to meter exposure when no operations are
performed. Choose from 4 s, 6 s, 8 s, 16 s, 30 s, 1 minute,
5 minutes, 10 minutes, or 30 minutes. The shutter-speed and
aperture displays in the control panel and viewfinder turn off
automatically when the exposure meters turn off.
Choose a shorter meter-off delay for longer battery life.

c3: Self-Timer

This option (available in all shooting modes) controls the length
of the shutter release delay (Self-timer delay; see right) and the
number of shots (Number of shots; choose a value from 1–9)
taken each time the shutter-release button is pressed in self-
timer mode (at values other than 1, pictures will be taken at the
rate selected for ! mode; pg. 182).
Option
Q 4 s
R 6 s (default)
S 8 s
T 16 s
U 30 s
V 1 min.
W 5 min.
X 10 min.
Y 30 min.
Self-timer delay
a 2 s
b 5 s
c 10 s (default)
d 20 s
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