Review by Klaus Schroiff, published May 2016

Introduction

As far as the mechanical quality is concerned, the Sigma 150-600mm f/5-6.3 DG OS HSM | Sports is, without doubt, a professional-grade lens. Everything screams quality here, but you also feel it ... in terms of weight. While the Tamron SP 150-600mm f/5-6.3 Di VC USD remains just below 2kg, the Sigma is rated at a whopping 2.86kg. That's not too much of a deal for those used to handle lenses such as a 400mm f/2.8, but normal mortals may be baffled upon first contact. So unless you intend to use a tripod, you better get ready for some extra sessions in the gym! The lens body is mostly made of metal with broad, rubberized zoom and focus control rings. Typical for such long zoom lenses, it extends substantially when zooming towards the long end of the range, but the inner lens tube doesn't wobble even at the most extreme setting. The lens is quite a sight at its 600mm, especially when attaching the deep lens hood - see below. Interestingly Sigma does not provide a lens cap. Instead, they supply a protective pouch for the lens hood. Our sample showed no significant amount of zoom creeping, but Sigma implemented a zoom lock that is functional at all zoom settings. The zoom action is slightly stiff, which is no surprise given the heavy lens groups that have to be shifted. The focus ring operates smoothly. A detachable tripod mount is included and is also needed when using the lens on a tripod. It is worth mentioning that the tripod mount plate is very big and, just to show attention to detail, it has not one mount thread but three.

The Sigma 150-600mm f/5-6.3 DG OS HSM | Sports features an optical image stabilizer ("Optical Stabilizer" (OS) in Sigma terms). I wasn't able to find an official figure regarding its efficiency. However, based on real-world experience with the lens, it seems to provide a gain of 3ish f-stops. UNLIKE its Tamron counterpart, the OS also works well at 600mm. Other than a general purpose OS mode, there's also a dedicated mode for panning.
Sigma's HSM (Ultrasonic AF) is very fast, accurate and virtually silent. The lens is also compatible with Sigma's (optional) USB Dock, so the lens' firmware can be updated without sending it to the Sigma service. In fact, the firmware was updated just prior to this review - enabling the lens to focus even a bit faster.

As you can see below, the Sigma 150-600mm f/5-6.3 DG HSM | Sports is substantially bigger than the Tamron SP 150-600mm f/5-6.3 Di VC USD - despite the same focal length and aperture range.