mk3 40d 400d and big white lenses

I dont know about you guys but i often stand my 300f2.8 and 500f4 on the hood ready to pick up and take a shot .
Now these cameras have vibration cleaning often whaen iv finshed shooting the camera is stoodup on the hood and i just turn it off (mk3 by the way )

SO is this a bad thing to do as any dust thats shaken off is just going to drop onto the back of the mirrow and not on the sticky colector .
i have only just thought about this .
Rob

being that the MkIII is weather sealed, I don't think dust during operation is an issue. I think if you pick the lens up, turn on the body, let the sensor clean, it'll be fine when you put it back down. Nothing's going to get in there after the camera is on.

As for the other bodies....I don't know. I just don't see it as an issue.

GyRob,
I have wondered about this myself with my 40D. When it does its auto cleaning I don't hear the shutter open. So does the dirt fall on the back of the shutter? Then again I haven't noticed any difference in dust on the sensor when using the auto clean or not (it really doesn't seem to do anything). Hmm..... I wonder?

Check this video out, it explains how the system works.