I went down to Sigma Singapore Office today wanted to calibrate a 2nd hand sigma lens which I brought from a member in clubsnap because of front focus although I can use my D7000 to AF fine tune, since I free today so I went down.
The lady at the counter told me that I need to call to meet appointment. (No walkin service). She told me they only provide ONE time free calibration per lens then will charge $150 per calibration after that. As for gray lens $150 calibration charge apply.
So just beware for those who's going to buy 2nd hand sigma lens.