Tamron 17-50mm f/2.8 XR Di II VC LD Aspherical IF SP AF

In September 2009, Tamron announced an update to its popular 17-50mm ƒ/2.8 zoom lens – the addition of an image stabilization system (Tamron’s ”Vibration Control” technology). Initially available only for the Nikon mount, a Canon mount became available in October 2009.

The lens is designed for the crop-frame APS-C sensor, meaning it will provide vignetted results if used on a full-frame camera. It uses a constant ƒ/2.8 design. On a Nikon body, the lens provides an effective field of view of 26-75mm; on a Canon body, 27-80mm.

The lens ships with a petal-shaped lens hood, takes 72mm filters, and is available now for approximately $650.

Sharpness

We noted some slight de-centering with the sample of the lens we tested. Sharpness results seem to be a little poorer than the original non-VC version of the lens; stopped down, it retains its excellent performance. Let’s look a little closer.

Wide open at ƒ/2.8, the lens shows some definite corner softness, mostly at wide angles. At 17mm, there is a nice central sweet spot of sharpness in the range of 1.5 blur units, but corner softness is significant in the top corners, escalating to upwards of 7 blur units. This is about as poor as it gets through, zooming in towards 50mm improves the corner performance, though (to some degree) at the expense of central performance. By 50mm at ƒ/2.8, the lens is producing images which are fairly sharp (around 3 blur units across the frame), but now are slight-soft corners are in the bottom of the frame, at 5-6 blur units.

Tamron 17-50mm f/2.8 VC, at 17mm and f/5.6.

As usual, stopping down does improve sharpness performance. However, especially noticeable at 17mm is a bit of uneven focus, which doesn’t really go away completely until ƒ/16. We could certainly chalk this up to a de-centered lens element and imagine that a better sample would provide us with better performance. At ƒ/5.6 at 17mm, there is a nice sharp sweet spot in the central range of the lens, but it’s still marred by considerable corner softness in the top left of the frame, and uneven focus in the bottom right.

Zoomed in, the lens provides a bit more stable performance, and at 50mm and ƒ/8, the lens shows excellent results for sharpness, providing just over 1 blur unit across the frame. Stopping down further doesn’t add much, and diffraction limiting begins to set in at ƒ/16. The lens stops down all the way to ƒ/32, providing even, if slightly soft results across the frame at around 3 blur units.

Chromatic Aberration

While CA is noticeable if you peep at 100%, for the most part it’s not a problem. It shows up mostly in the corners when stopped down to ƒ/8 or smaller – except at 50mm, where (curiously) it’s more prominent at larger apertures.

Shading (”Vignetting”)

The Tamron 17-50mm ƒ/2.8 VC provides consistent corner shading from one focal setting to the next – there is some light falloff when used at wider apertures (between 2/3 and 1 full stop at ƒ/2.8, and a half to 2/3 of a stop at ƒ/4, depending on the focal length). By ƒ/5.6, corner shading is very low, with the corners of the image a quarter-stop darker than the center, or lower.

Distortion

Tamron has improved upon the distortion control for this lens. While there is some barrel distortion with the lens used at its widest angle (1% in the corners, 0.6% on average) this is to be expected. The distortion decreases gracefully as the lens is zoomed in to 35mm, evening out to essentially 0% between 35mm and 50mm.

Autofocus Operation

Autofocus is conducted electrically, without the use of a mechanical screw. Autofocus speed is fairly quick, producing a slight noise during focusing, but nothing objectionable. Focus speed is not as quick as that seen on Canon’s USM or Nikon’s AF-S technologies, and isn’t as quiet, either. The lens will autofocus on the ”screw-less” Nikon D40, D40x and D60 bodies. The front element doesn’t rotate during focus operations, making the use of a polarizing filter that much easier.

Macro

Macro isn’t much to write home about – just 0.21x magnification, with a close-focusing distance of just over 11 inches (29 cm).

Build Quality and Handling

The Tamron 17-50mm ƒ/2.8 VC is composed of mostly plastic, with a metal lens mount. Despite being a lens designed for the smaller APS-C sensor, it’s quite a handful, and fairly heavy for ths size. The lens sports an all-black matte finish. The lens has a locking switch for keeping the lens at the 17mm focal length setting. There is a switch to activate and deactivate vibration control, as well as activating or deactivating autofocus. The lens has a distance scale, but no depth of field markings.

The zoom ring is the larger of the two, rubber with ribs, just over an inch wide. The ring is very smooth, firm but not too tight, requiring two fingers to move. There is some slight lens extension (1 1/4”) as the lens is zoomed in to 50mm, and owing to this, we didn’t find any evidence of zoom creep. It could be as the lens is worn in the zoom could become a little more slippy, but in this eventuality, Tamron has thoughtfully provided a switch to lock the zoom at 17mm. It takes about 90 degrees of turning action to go from 17mm to 50mm.

The focus ring is just 3/8” wide, using the same rubber texture but slightly different ribs. The lens was not really designed with manual focusing in mind, with just 45 degrees of focusing action. The lens focuses past infinity, and there are hard stops on either end of the focusing spectrum.

We have done some testing on the vibration control feature of this lens, and we hope to update this review shortly with the results of that testing.

The lens hood for the 17-50mm ƒ/2.8 is the petal type, adding an extra 1 5/8 inches to the length of the lens when mounted. The hood is flocked on the interior, and reverses to mount on the lens for storage.

Alternatives

Tamron 17-50mm ƒ/2.8 XR Di II LD Aspherical IF SP AF ~$400
The real question most people will be asking is how the new lens compares with the older version. In a nutshell, while the new lens provides vibration control functionality, the old lens provided better results for sharpness, resistance to chromatic aberration and corner shading; distortion is noticeably improved.

Sigma 18-50mm ƒ/2.8-4.5 DC OS HSM ~$200
While the Sigma 18-50mm isn’t a constant ƒ/2.8 lens, it does provide Optical Stabilization. It can’t offer ƒ/2.8 at the same focal lengths as the Tamron, but where the lenses overlap at aperture, the Sigma is as sharp or sharper – except at the wide end. At 18mm, it doesn’t quite match the Tamron. CA performance and distortion control also aren’t as good as the Tamron; corner shading is slightly better.

Canon EF-S 17-55mm ƒ/2.8 IS USM ~$1000
There really isn’t much of a contest between the Canon and Tamron lenses – for a few hundred dollars more, the Canon lens is sharper, though its distortion profile and resistance to CA is a bit worse. Corner shading is about the same. The build quality is much higher with the Canon, and autofocus speed is much faster.

Nikon 17-55mm ƒ/2.8G ED-IF AF-S DX Nikkor ~$1350
Similarly, the Nikon 17-55mm is a pro-caliber lens. In this case however the Nikon lens does not feature image stabilization, and its results for sharpness, while a little more ”even” than the Tamron, are not head-and-shoulders better. CA performance is similar, perhaps a little better on the Tamron (in the corners). Distortion is better-corrected in the Tamron. The Nikon fares much better against corner shading.

Conclusion

Tamron seems to have had to make some sacrifices to add Vibration Control to its popular 17-50mm ƒ/2.8. It’s not bad with regard to sharpness, just not as good as the non-VC version, leading potential buyers to decide how badly they need Vibration Control.

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.

(From Tamron lens literature) Tamron USA, Inc. has announced the release of the SP AF17-50mm F/2.8 XR Di II* VC LD Aspherical [IF] (Model B005), a high speed ƒ/2.8 wide-to-moderate-telephoto zoom lens designed exclusively for Nikon-mount digital SLR cameras with smaller sensors. Featuring Tamron’s proprietary tri-axial Vibration Compensation (VC) mechanism that minimizes the effects of handheld camera shake, the lens will be available starting on September 17, 2009. Tamron plans to introduce the lens in a Canon mount version shortly after the new Nikon mount version with built-in motor hits the market.

The new SP 17-50mm F/2.8 XR Di II VC covers the very popular 17-50mm focal length range (equivalent to 26-78mm in the full-frame 35mm format**) making it extremely versatile. Its wide aperture and outstanding performance provide practical advantages in low-light shooting and aesthetic image control, thereby enriching the user’s range of creative expression. The new lens delivers impressive sharpness and striking contrast over its entire focal-length and aperture range, and at its maximum aperture of ƒ/2.8 it produces beautiful images enhanced by shallow depth-of- field, and smooth, natural transitions in out-of-focus areas of the image (i.e. excellent bokeh.) The new lens is equipped with Tamron’s proprietary Vibration Compensation (VC) image stabilization mechanism, which controls the effects of camera shake in three planes. VC provides more opportunities for sharp hand-held photography at the slow shutter speeds needed when shooting in low-light conditions (e.g. night or indoor scenes) dramatically enhancing the user’s level of photographic freedom.

The previously announced, still currently available Tamron SP 17-50mm F/2.8 XR Di II (Model A16) boasts superlative optical performance for a fast standard zoom lens and has been acclaimed world-wide as a masterpiece of compact optical design. In developing the new Tamron SP 17-50mm F/2.8 XR Di II VC zoom, the primary goal was to maintain this incredible compactness and ease-of-use while simultaneously enhancing its convenience and expanding its performance envelope. As a result of concerted efforts, the engineers were able to incorporate Tamron’s proprietary state-of-the-art Vibration Compensation (VC) image stabilization mechanism into the new lens without materially increasing its size and weight. As a result of this success, the SP 17-50mm F/2.8 XR Di II VC makes sharp hand-held photography possible under a vastly expanded range of photographic situations.

The Tamron Vibration Compensation mechanism employs a three-coil system in which three driving coils move internal optical components within the VC lens electromagnetically, based on signals originating from three steel ball bearings. Since the VC compensating lens elements are held in place solely by contact with these bearings, smooth, virtually frictionless movement is assured, providing the stabilized viewfinder images and excellent tracking performance characteristic of VC lenses. Moreover, since the VC lens elements move parallel to the image plane via electronic control alone, the mechanical structure is simplified, and the lens is more compact.

*Di (Digitally integrated)-II lenses are designed for exclusive use on digital cameras with smaller-size imagers. This lens is not designed for use with 35mm film cameras or digital SLR cameras with image sensors larger than 24mm x 16mm.

**Tamron’s conversion value is 1.55x