Question about Sigma APO 50-500mm F4-6.3 EX DG/HSM Lens
That is some heavy glass.. it sounds like there is a problem with the drive mechanism in the lens when the lens is extended. The droop from the weight of the glass prevents the mechanism to function as designed.
Since this is a precision optic, I would send it to Sigma or other reputable shop for a repair estimate. Attempting to disassemble this or contaminating interior parts would worry me too much for me to try it. Unless you know what you're looking for - I'd arrange for service by calling (1-800-896-6858) or contacting Sigma Customer Support, package it up and send it out for repair. You might still be under warranty, too.
Posted on Mar 23, 2011
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Posted on Jan 02, 2017
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