silent pic firing with too many buttons

[ToniX]

I am playing with silent pic feature (very intriguing feature indeed) I only have a problem:

I found that it fires either when half pressing the shoot button,  but also when pressing the zoom- button.... and also when pressing the camera DOF button. Is it a feature?

Is it possible to assign silent pic shooting to just one button  (possibly not the zoom- one, since zooming is very commonly used just for precise focus checking).

Thanks for help