Nikon D300 User Manual page 733

When you press the Shutter-release button down and take a
picture in Q mode, the mirror raises and the shutter fires.
However, the mirror does not lower until you fully release the
Shutter-release button.
If you want to reduce noise, you can hold the Shutter-release
button down longer than normal and separate the raising and
lowering of the mirror into two steps. This tends to draw out
the length of the mirror/shutter action and reduces the
perception of noise volume. In reality, the noise is not much
quieter, but since it is broken into two parts, it sounds quieter.
Try it!
Live View (Lv) Mode (D300 only)
Live view mode (Lv) uses the Monitor to display the subject
instead of the Viewfinder. We'll examine using autofocus in
Live view mode later in this chapter.
Self-Timer Mode
The factory default time out for the Self-timer is 10 seconds.
You can use Custom setting C3 to set the time out to 2, 5, 10,
or 20 seconds.
If you like to hear that little "beep beep beep" when the
Self-timer is counting down the seconds before firing the
shutter, you can control that sound with Custom setting d1 by
selecting High, Low, or Off. If you select High or Low, a
small musical note will appear in the top right of the Control
panel.
733