I just got the new 100mm IS L Macro lens to pair up with the T2i. When I press the shutter half way down, in addition to autofocussing, the lens makes a hissing noise for a few seconds. This is probably the IS running. Then if I move it a little bit, there is another noise which is probably the lens trying to stabilize. Is this hissing noise normal? This is my first lens of this type so I do not know if this is normal. It takes great pictures but I am just learing how to use it.


Thanks -