With the advent of sensor cleaning in newer bodies - does it matter which way up you hold the camera whilst it is cleaning? I understand that the sensor cleaning works by vibrating the sensor to knock the dust off, to stick to a "very sticky bit" - but are these very sticky bits all around, or only below the frame in landscape orientation?
This article on Pixinfo talks about a test that they have made between for cameras with sensor cleaning systems. According to that, the camera has to be upright for the sensor cleaning to be effective.
However, the test also suggests that for some cameras it doesn't matter much, because the sensor cleaning hardly works at all.
I was watching a video about the 645D and the Pentax rep mentioned, in the course of the interview, that when doing dust removal it is best to hold the camera in landscape orientation as level as you can to get the most optimal outcome. He also mentioned that it applied to all dSLR cameras with sensor shake dust removal, not specifically the Pentax ones. So... Since then, that's how I do it and I do it every time I swap lenses, seems to be working for me, I've had very little problems with sensor dust.
YES. It matters.
This is because the camera has a slight sticky pad at the bottom of the camera so when the sensor vibrates it will fall on to this little pad. If the camera is on its side or pointing up you just moving the dust around. If pointing down it just falls into your lens or mirror just to end up back on the sensor.
I imagine that if you were to orient the camera directly downwards, you would get the most effective "drop off" effect due to gravity, however the dust would then drop onto the shutter, and probably find its way back onto the sensor very quickly.
I just place mine upright on a table and let it do its thing.