Sigma 50-200mm f/4-5.6 DC OS HSM

SLRgear Review
October 27, 2009
by Andrew Alexander

At PMA2009, Sigma announced an update to their telephoto zoom lens, in the form of the 50-200mm ƒ/4-5.6 DC OS HSM. The previous version of the lens was a 55-200mm zoom, upgraded once to incorporate an in-lens motor, and then again to provide optical stabilization.

With its DC specification, the lens was designed specifically to fit the APS-C sensor, making it incompatible with film or full-frame digital camera bodies. On a Canon body the lens offers 80-320mm range; on Nikon and others, the lens offers 75-300mm range. This lens isn't a "constant" lens, in that as you increase the focal length, the largest aperture rating increases. The following table reflects the changes:

The lens ships with a circular-shaped lens hood, takes 55mm filters, and is available now for approximately $300.

Sharpness
The lens is respectably sharp between 50 and 100mm; longer than this, and image sharpness drops off.

Wide open at 50mm and ƒ/4, the lens does quite well at around 1.5 blur units, with one soft corner in the upper right hand side. Stopping down only offers marginal improvements, most notably smoothing out the errant corner. By ƒ/8 the image is as sharp as it will get, still around 1.5 blur units. Performance is similar up to and including 100mm: the right side is notably softer than the left, suggesting to us the lens is slightly de-centered.

Above 100mm, the lens shows a nice sweet spot of sharpness in the near-center, but again, de-centering shows off a soft corner, the right, where we note almost 5 blur units at 135mm. Stopping down helps here, and again, things even out around ƒ/8-ƒ/11 where the image shows between 1.5-2 blur units. At 200mm the lens is pushed to its limit, showing uneven focus when used wide open at ƒ/5.6, and performance ranging from 2 to 5 blur units across the frame. Stopping down to ƒ/8 tames the uneven-ness, but that's about as good as it gets - there's no additional improvement from stopping down further (~2-3 blur units).

Fully stopped-down performance is best avoided; while relatively good at wide angle (~3 blur units at 50mm and ƒ/22), smaller apertures quickly degrade, until we note 5-6 blur units at 200mm and ƒ/32.

Chromatic Aberration
Where the Sigma 50-200mm ƒ/4-5.6 OS offers fairly good results for sharpness at 50mm, CA is fairly notable. It's not bad at ƒ/4, but at ƒ/8 and smaller it's particularly noticeable. It's at its worst at 50mm; at other apertures, it's actually fairly good.

Shading (''Vignetting'')
Corner shading isn't much of a factor for this lens, with only a 1/3-EV difference between the corners and the center when used wide open at any focal length. At any other focal length and aperture setting, corner shading is negligible.

Distortion
Distortion results for the Sigma 50-200mm ƒ/4-5.6 are typical for this class of lens, showing a complicated mix of both barrel and pincushion distortion in the longer range of its telephoto focal length. Between 50-67mm, distortion is slightly barrelled, at +0.4% in the corners; the lens reaches a kind of parity around 62mm. After this point, the corners show pincushion distortion while the central region shows some slight barrel distortion. At its worst, we note almost -0.5% pincushion distortion in the corners above 100mm; similarly, almost +0.2% barrel distortion distortion throughout the image above 100mm.

Autofocus Operation
The lens uses Sigma's hypersonic motor (HSM) technology, offering quick and quiet autofocusing. Despite having a relatively short focusing throw (around 50 degrees), the lens isn't as fast as some of Sigma's other designs, taking around 1.5 seconds to go from infinity to close-focus. In its favor, the front element doesn't rotate as it did in previous versions of the lens.

Macro
The lens doesn't offer exceptional macro performance, with just 0.22x magnification and a minimum close-focusing range of 110cm (over three feet).

Build Quality and Handling
The lens is built with economy in mind, and features an all-black, all-plastic construction. The lens is coated with Sigma's rubberized coating, which offers good traction - the lens won't slip out of your hands any time soon. There are two switches on the lens, one to activate or deactivate image stabilization, and one to enable or disable autofocusing. The lens features a distance scale, but doesn't offer a depth-of-field scale. The lens mount is metal, and the 55mm filter threads are plastic.

The focus ring is mounted at the end of the lens, 1/2-inch wide and composed of raised rubber ribs. As mentioned, the focusing range of the ring is fairly small, only 50 degrees, making manual focusing a bit tedious. The focusing throw is bounded on either side by hard stops. The lens will focus slightly past infinity. Thanks to a new internal focus design, the front element doesn't turn while focusing.

The zoom ring is the larger of the two, 3/4-inch wide, also composed of raised rubber ribs. The lens gets almost an inch longer (7/8") as the lens is zoomed in to 200mm. There is around 75 degrees of rotation in the zoom ring, and a nice level of resistance to the ring; not too tight, and not too loose. There's no evidence of zoom creep, and Sigma is confident enough in their design that they didn't include a zoom lock.

Optical image stabilization is included in this lens, making it an obvious improvement over the previous 55-200mm versions. We test this feature separately, but in informal testing we can say that it does work well, though whether it reaches the claim of four stops of hand-held improvement is another matter.

The included lens hood is of the circular design, adding a further 1 1/2 inches to the overall length of the lens. The interior of the hood is deeply ribbed to reduce the impact of any stray light entering the front element, and the hood can be reversed onto the lens for storage.

Alternatives

Pentax 50-200mm ƒ/4-5.6 ED SMC P-DA ~$200
Where the Sigma performs well at 50mm, our evaluation of the Pentax 50-200mm showed only average performance at 50mm; in other areas, the Pentax meets or exceeds the sharpness of the Sigma. The Sigma handles CA better than the Pentax, as well as providing less corner shading and slightly better results for distortion. Pentax bodies have image stabilization built-in, so you won't be buying it for the OS feature.

Tamron 55-200mm ƒ/4-5.6 Di II LD Macro AF ~$120
Available in Canon, Nikon and Sony (Minolta) mounts, we haven't tested the Tamron equivalent, though without image stabilization, it's notably cheaper than the Sigma.

Canon EF 55-200mm ƒ/4.5-5.6 II USM ~$170
The lens isn't one of Canon's finer designs, and the Sigma is noticeably sharper at all focal lengths (especially 200mm). It's marginally better at handling CA; distortion and corner shading are about the same. The Canon can fit on a full-frame body; the Sigma comes with image stabilization.

Canon EF-S 55-250mm f/4-5.6 IS ~$250
Canon's APS-C variant of the above, the lens is about as sharp as the Sigma - until you get to the higher end of the telephoto range, where the Canon proves to be sharper. It shows a bit less CA and distortion as well, though there's a bit less corner shading in the Sigma. For the price though, it seems the Canon is the better buy all-around.

Nikon 55-200mm ƒ/4-5.6G IF-ED AF-S DX VR Nikkor ~$220
The Nikon lens is noticeably sharper than the Sigma, in fact, it's one of the sharper consumer-level lenses we've tested. CA is also handled very well; however, distortion is a little bit more complex with the Nikon, and corner shading is high. Both lenses feature optical stabilization.

Sony 55-200mm ƒ/4-5.6 DT ~$220
The Sony 55-200mm is about as sharp as the Sigma; CA is fairly well-handled, interestingly the better performance shows at the wider (55mm) end in contrast to the Sigma. Corner shading and Distortion results are better in the Sigma, but not by much. Sony bodies feature image stabilization, so like Pentax users, Sony users won't be buying it for this feature.

Conclusion
While the obvious alternative is the non-OS Sigma 55-200mm ƒ/4-5.6, we haven't tested it so we can't speak to whether or not Sigma has improved on the original package. Used wide open it's above average, stopped it down to ƒ/5.6 or ƒ/8 and it provides good performance. With internal focusing and optical stabilization, there's a lot to like about the new lens, especially considering the low price tag.

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.