I have noticed that when you push the Auto/Manual button
to Manual all the Auto settings are still active and the Zoom
can now be also activated with the Focus Ring on the lens,
as it defaults to Manual Zoom. In the Manual Mode the
Zoom Lever on top of the GS400 will still work together with
Focus Ring Zoom and you will get access to Picture Adjustment
to enable Sharpness and Colour Levels of the picture. Therefore
I cannot see why one should use the Auto setting when you get
less options available in this mode.

Soft Skin Button activated can result in a softer picture,
and it is important that before turning on the power, remove
the Lens Cap. If the Lens Cap is still attached when the
power is turned on, Automatic White Balance Adjustment may
not function correctly as the Manual states.

>>Therefore I cannot see why one should use the Auto >>setting when you get less options available in this mode.

Non experienced user auto setting, the people knows what to do manual mode. 8 )

Here is my recording of the silent:
http://www.videomax.ru/tests/gs400/silence-GS400.wav (1380k). You can compare.