Designed for the professional sports and wildlife shooter, the Sigma 500mm f/4 DG OS HSM Sports features a rounded 9 blade diaphragm which creates an attractive blur to the out of focus areas of the image, an Optical Stabilizer system that compensates for up to 4 stops of shutter speed with an accelerometer for improved vertical and horizontal panning, an Hyper Sonic Motor for fast and quiet autofocusing, manual override (MO) which is activated by rotating the focus ring while usingBut Sigma has developed a lot of confidence in recent years, and so they jumped into the fray with a lens they call their "flagship" lens – the Sigma 500mm F4 DG OS HSM Sport (hereafter referred to as the 500S for brevity)SIGMA 500mm F4 DG OS HSM Sports on Nikon D800 – 1/4000s, F4, ISO 1000 The quick, quiet and accurate focusing is the reason I use this lens most, but there's more to love about the 500mm F4 Sports The beautiful separation it creates between subject and background — from F4 unti