I returned the first copy because the OS seemed not to work and this copy is much better right out of the box and seems to be working just fine.However I picked up the USB dock and took it a couple steps further. First a firmware update was found and then I also changed the OS to Dynamic which is the best of the OS. I also changed the AF to the fastest setting and what a huge difference it makes after I rewrote the firmware to one of the custom mode settings on the lens. If anyone get this lens do get the dock,it is well worth 60 bucks. Bravo sigma for the dock.By the time I unpacked everything it was dark so will have to sharpness test on first light.