CameraControlProperty HTC-Prodigy

I am trying to use the IAMCameraControl CameraControl_Zoom property on an HTC-Prodigy device (SPV M3000 or whatever it is called here). The range I get is valid (min=1, max=2, step=1). I can set the property to 1 or 2, meaning when I read it out with a "get" it's all good, but it just does not have any effect in my capture app. I can see that the internal camera application can set the zoom to 1 or 2.
What do I have to do to make the zoom setting actually being applied to the (running) camera / graph? I can set it before or after the graph is constructed or run, same effect, so I guess stopping / starting would not help.

Cheers,
Andres
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