Nikon D3300 Reference Manual page 92

4
Take the photograph.
Press the shutter-release
button halfway to focus,
and then press the button
the rest of the way down.
The self-timer lamp will
start to flash and a beep will
begin to sound. Two seconds before the photo is taken, the
lamp will stop flashing and the beeping will become more
rapid. The shutter will be released ten seconds after the timer
starts.
Note that the timer may not start or a photograph may not be
taken if the camera is unable to focus or in other situations in
which the shutter can not be released. To stop the timer
without taking a photograph, turn the camera off.
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