When I bought the Sigma 150-600mm F5-6,3 DG OS HSM Sport Lens almost a year ago I was literally blown away by the picture quality. What amazed me most was the fact that I was almost unable to detect any quality degradation when moving towards the 600 mm end. However this impression changed dramatically when using the lens in combination with the 1.4 Extender from Sigma. There was no way I would be able to get a single somewhat sharp image with this combination of lens and extender. Now Sigma has published a firmware update (V1.3) for the lens that is supposed to address exactly this issue. I have tested the update with my lens on a Canon EOS 5D Mark III and I can confirm that the AF quality and performance is much better after applying the firmware update.