If extremely precise autofocus is required, this calibration dock will fine-tune the relationship between the specific camera and the specific Sigma lens you are using. For ultra precision, you may want to also hire the Datacolor SpyderLENSCAL calibration chart, see accessories.
By connecting the USB cable to a computer, Sigma USB Dock enables photographers to update the lens firmware and adjust parameters such as focus. It is designed for use with the new Contemporary, Art and Sports product lines. The adjustment is processed with special software (Sigma Optimization Pro). The AF speed, focus limiter and OS function are also customisable for Sports lenses.