Hey i just brought a Second hand EF-S 17-85 F/4-5.6 Lens and i realize there is a Jazz sound whenever i Half tab my shutter button and after i full tab my shutter button. Can some one explain to me Why ?? BTw not a very Big issues rite cos the previous owner claim that she had use this lens for 2 year and just gone for servicing in April 2010 in addition i had already check the IQ and the overall appearance 8 /10. Only haven went out to test the lens.