Just calibrated my lens few days ago, now very sharp even at open wide.
I bought my lens from HK and it has international warranty.
But Sigma SG told me that they only honour the parts only, the labour you still need to pay (e.g. for calibration you need to pay $80).
So I argue, from the customer point of view, how do we know if the shop in HK is sigma official/non-official since the lens comes with international warranty?
At the end, she allowed me to calibrate my lenses (30mm + 50mm) for free... but she mentioned next time I have to pay for the labour.
Also, she mentioned that if the lens bought in SG, the warranty would be 2.5 years (instead 1 year if bought in HK).