Sigma 70-200mm f/2.8 EX DG OS HSM APO

SLRgear Review
October 10, 2010
by Andrew Alexander

Announced at PMA 2010, the Sigma APO 70-200 F2.8 EX DG OS HSM is the fourth iteration of its telephoto zoom competitor, the chief innovation being the addition of Sigma's OS (Optical Stabilization) feature. To accommodate this, the optical structure of the lens has been redesigned, adding four new lens elements in two groups; as well, the lens is slightly longer (1/2'') and heavier (2 oz).

The lens features a constant ƒ/2.8 aperture, and was designed to fit film or full-frame imaging sensors. On a sub-frame digital camera body, the lens will provide an equivalent field of view of 112-320mm (Canon) or 105-300mm (Nikon and others).

The lens ships with a petal-shaped lens hood and tripod mount, takes 77mm filters, and is available now for around $1,700.

Sharpness
The Sigma 70-200mm ƒ/2.8 OS provides exceptionally sharp results, even with a very wide aperture setting, between 70-135mm; at 200mm, it's not as sharp.

When mounted on the sub-frame 7D, the lens returned very sharp results at 70mm and ƒ/2.8; just under 1.5 blur units in the center, and just over 1.5 blur units in the corners. Stopping down to ƒ/4 offers some improvement to central sharpness, where it reaches 1 blur unit, but still 1.5 blur units in the corners. At ƒ/5.6, it's tack-sharp at 1 blur unit across the frame. This sharpness is maintained until ƒ/11, where diffraction limiting begins to set in, but edge-to-edge sharpness results of under 1.5 blur units are noted. We note just under 2 blur units across the frame at ƒ/16, and just over 2 blur units at ƒ/22.

These results are essentially repeated at focal lengths up to 135mm; at 200mm, there's a marked difference. At 200mm and ƒ/2.8, there is a very small central spot of sharpness (~1.5 blur units) but corners reach the level of 3 blur units. Stopping down does help, showing at ƒ/4 what other focal lengths show at ƒ/2.8 - 1.5 blur units in the center, and in this case, just over 2 blur units in the corners. Sharpness results stay at 1.5 blur units at ƒ/5.6 and ƒ/8, and then degrade at ƒ/11 and smaller.

Mounted on the full-frame 1Ds Mark III, sharpness results follow essentially the same trend as noted on the sub-frame 7D, with notably softer corners. Instead of ƒ/5.6, the sharpest results are obtained at ƒ/8, but with the exception of 100mm, we never see ''tack-sharp'' results from corner to corner.

Chromatic Aberration
For the most part, CA is kept nicely under control with the lens mounted on the 7D. With the lens set at ƒ/5.6 and smaller at 200mm, CA becomes somewhat noticeable in areas of high contrast. With the lens mounted on the full-frame 1Ds Mark III and set to 70mm and ƒ/2.8, CA is slightly more prominent in the corners when compared to the 7D.

Shading (''Vignetting'')
With the 70-200mm ƒ/2.8 OS mounted on the 7D, corner shading isn't really a factor. On the full-frame 1Ds Mark III however, corner shading is noticeable: at ƒ/2.8 the corners are around 2/3 EV darker than the center. At ƒ/4, the corners are around 1/3 EV darker. At ƒ/5.6, the corners are 1/4 EV darker, or less, as the aperture is stopped down.

Distortion
Distortion is well-controlled by the Sigma 70-200mm OS. On the 7D, distortion isn't much of a factor, with some barrel distortion at 70mm (just under +0.2% in the corners) and turning into pincushion distortion at 200mm (around -0.2%). There is a point of parity (neither barrel nor pincushion around 90mm).

On the full-frame 1Ds Mark III, it's the same general trend, but distortion is slightly more exaggerated: on this body we note +0.5% barrel distortion in the corners at 70mm, and -0.6% pincushion distortion at 200mm. Again, there's negligible distortion at around 90mm.

Autofocus Operation
Using Sigma's HSM autofocusing technology, autofocus results are quick and near-silent, taking just over 1 second to go from close-focus to infinity. Point to point focusing happens very quickly, and the front element does not rotate during autofocus operations. Autofocus results can be overridden at any time by simply turning the focusing ring.

Macro
With just 0.13x magnification, the Sigma 70-200mm ƒ/2.8 OS does not offer exceptional macro performance. Minimum close-focusing distance is about 4 and a half feet.

Build Quality and Handling
The lens is a fairly complex design with 22 elements in 18 groups, including three super low-dispersion and two elements of Sigma's latest technology, ''FLD''. It wouldn't appear that these elements are not actually composed of fluorite because Sigma indicates that the elements offer performance ''equal to fluorite glass.'' It's solid - just over three pounds of lens, coated with a textured finish with makes it very easy to handle. The diaphragm consists of nine rounded aperture blades. The body mount is metal, and the filter mount is plastic.

The lens has two switches to speak of, including one for disabling autofocus and another for selecting the optical stabilization mode. Stabilization can be set to vertical and horizontal, or vertical only, to allow for panning shots. Optical Stabilization can also be disabled with this switch. A windowed distance scale shows distance information in feet and meters; there is no infrared index marker, but there are depth-of-field markings on the lens. This is something of a rarity on zoom lenses, as the depth-of-field will change based on the zoom setting; in this case there is are depth-of-field markings for ƒ/5.6, ƒ/11, ƒ/16 and ƒ/22 at the 70mm (''W'') setting, and a single marking of ƒ/22 at the 200mm (''T'') setting.

Sigma has redesigned the zoom and focusing rings on this lens, with quite a departure from the previous three iterations in the 70-200mm series. The position of the rings is reversed, and the focusing ring is much smaller than in the previous models.

The zoom ring, located at the fore of the lens, is the wider of the two at 1 1/2'' wide. The ring is composed of rubber, with large raised ribs. It takes a twist of around ninety degrees to go from 70mm to 200mm, and the ring is nicely smooth to turn. There is no evidence of zoom creep.

The focusing ring is integrated into the middle of the lens, and is just 3/8'' wide. The texture is similar to the zoom ring - rubber, with raised ribs. The ring turns quite smoothly, and ends in soft stops on either side of the focusing spectrum (ie., you can keep turning the ring, but an increase in pressure lets you know you won't continue focusing). There are about 120 degrees of turning fidelity, making it fairly easy to manually focus the lens. Attached 77mm filters won't rotate during focus operations.

The lens hood for this lens features a new design, as well. It's a standard petal-shaped lens hood, and is fairly long, adding four inches in length to the lens when attached. The novel design is that Sigma has included an adapter that extends the depth for use with sub-frame (APS-C bodies), which adds an extra inch to the overall length of the hood. With our without the adapter attached, the lens hood reverses and attaches onto the front of the lens for storage.

For image stabilization performance, please check the tab above marked 'IS Test'. To summarize, the lens lives up to its manufacturers' claims, offering 4 stops of image stabilization at 70mm, and 2-2.5 stops at 200mm.

Alternatives

The Sigma 70-200mm ƒ/2.8 OS is offered in several different mounts: Sigma, Canon, Nikon, Sony and Pentax. Since Sony and Pentax cameras have image stabilization incorporated into the body, users of those cameras may not feel a strong attraction to the stabilization feature of this lens.

Sigma 70-200mm ƒ/2.8 II EX DG Macro HSM APO ~$800
We haven't tested the previous iteration of the Sigma 70-200mm ƒ/2.8 lens, but our tests of a version previous to that showed it as being on par with anything that the other major manufacturers had to offer. The build quality isn't quite at the same level - Sigma doesn't offer weather sealing, for example - but if you have no need for image stabilization, you will save a lot of money.

Canon EF 70-200mm ƒ/2.8L IS II USM ~$2,300
The Canon 70-200mm ƒ/2.8 is just that little bit better than the Sigma in every category - sharper, especially at 200mm, and image stabilization results at 200mm are significantly better as well. You'll pay significantly more for the Canon than the Sigma, but it's probably worth it for the increase in performance.

Nikon 70-200mm ƒ/2.8G AF-S ED VR II ~$2,250
Similarly to the Canon, the Nikon 70-200mm ƒ/2.8 is sharper than the Sigma, also offering better results for CA, and corner shading. Distortion is better at 70mm, but the Nikon is slightly more distorted at 200mm, choosing to optimize distortion results at the wider end. We haven't yet done an IS test for this lens.

Sony 70-200mm ƒ/2.8 G SAL-70200G ~$1,800
Performance between the Sony and Sigma lenses is comparable, but the Sigma is slightly sharper at ƒ/2.8 (our sample of the Sony didn't offer exceptionally sharp images at ƒ/2.8). Results in other test categories are comparable, except the Sony may offer slightly better results for distortion.

Pentax 50-135mm ƒ/2.8 ED AL IF SDM SMC DA* ~$800
Pentax no longer offers a directly comparable lens, but the closest would be this one, offering an equivalent 75-202mm field of view. We haven't yet tested this lens.

Conclusion
Sigma has figured out that to compete with the major manufacturers, it has to offer optical stabilization, and it makes excellent sense to implement it into this particular category of lens. Our sample of the lens offered very good performance at ƒ/2.8 - unfortunately the one area it could really do better would be at 200mm, where I'm sure the lens would be used extensively. The results of our image stabilization testing show that Sigma has invested a lot of time in this new process; four stops at 70mm, and 2-2.5 stops at 200mm. There's still room for improvement, as there is some wandering in the viewfinder, but I'm sure the feature will be widely appreciated.

The real question in the end will be the price point. Sigma's previous versions of this lens sold for under $1,000; new FLD lens elements, optical stabilization and a complete exterior redesign has increased the price tag by $700. For a few hundred dollars more, Nikon and Canon shooters can have brand-loyal versions of the lens; Sony and Pentax users probably won't be awed by the addition of optical stabilization, as every lens they shoot with is effectively image stabilized with their cameras' body-based stabilization.

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.