I have a canon 70-300mm IS USM, I noticed that when the IS is on and when the shutter button is half pressed, the lense makes noise, that is the image stabilizer kicking in and the noise persists until about 2 to 3 seconds after the shutter button is released. Though the noise is not very apparent, you need to hear it with the lens close to your ears. It is a faint hissing/grinding/cluttering noise.
This problem (should I call it a problem?) seems to be a common one with most of the canon's telephoto lense. But the surprising fact is that none of the renowned reviews speak about it.
I was bit worried when I got the lens, then I went to the Jessops and checked with couple of other IS lens and and an identical one, they too make the noise, in fact the person in Jessops was taken by surprise by the noise.
If anyone has encountered with IS noise can you please share your experience?