Enewsletter
June 2010

To find out how all these expectations worked out in the real world, I spent two weeks taking pictures with this innovative lens under a wide variety of shooting conditions, from casual portraits and grab shots in the extremely low light encountered in coffee houses and pubs to scenic and architectural views and floral abstracts taken in brilliant sunshine. Here’s what I found over the course of my adventures.

This grab shot was taken wide open at f/2.8 and 1/250 sec at the 26mm (40mm equivalent) focal length setting. It’s sharp, but detail is somewhat softened by “digital grain” at very high ISO setting of 6400.

The Tamron 17-28mm f.2.8 VC is relatively compact for a lens of its speed and focal length, measuring 3.7 inches in length at the 17mm position, with a diameter of 3.1 inches. However, achieving a high degree of optical correction along with a very wide constant aperture required a 19-element 14-group design employing large—diameter glass, including LD (Low Dispersion glass) and compound aspheric elements. The result is a lens that’s somewhat heavier than it looks—20.2 ounces. Fortunately it is hefty rather than ponderous, and it balances extremely well on both my lightweight Canon T21 and middleweight 50D bodies.

Its textured, easy-to-grasp 1-1/8-inch-wide zoom ring takes the lens from 17mm to 50mm in a smooth, well-damped 90-degree clockwise turn, thereby extending the front of the lens an additional 1-3/4-inches. However its mass is so well centralized that most of its weight is carried near the middle of the barrel so its excellent handling and stability are not compromised even at the 50mm setting. The lens uses an IF (internal focusing) system, which has the advantage of maintaining high image quality at very close focusing distances. While not a true macro lens, or labeled as such, the 17-50mm VC gets down to a respectably close 11.4 inches at all focal length settings, yielding a near-macro maximum magnification ratio of 1:4.8 at the 50mm setting. This is certainly close enough for frame-filling headshots of people (including babies), but not quite close enough to document your coin collection or get scary-looking close-ups of tiny insects. Another plus is its very small minimum aperture of f/32, not all that common in mid-range zooms. This allows you to achieve an extremely broad depth of field, especially at the wide-angle settings, but also at 50mm. By selecting f/32 and focusing at an object located at a near or middle distance you can capture sharp image detail from under a foot from the camera all the way to infinity, a great visual effect for dramatic landscapes and environmental portraits. There is inevitably a slight loss of sharpness due to optical diffraction at f/32, but overall image quality holds up remarkably well and you probably won't notice the difference.

Abstract of railcar wheel overgrown with vines was shot at f/2.8 and 1/250 sec, ISO 100, 26mm (40mm equivalent) focal length setting. Note exquisite sharpness, contrast, and detail at the precise point of focus (3 bolts on Timken axle cap).

When shooting handheld I kept the VC turned on all the time. The clearly labeled, positive action VC and AF on-off switches are conveniently located on the left side of the rear of the lens barrel with the lens mounted on the camera. The only time you need to turn VC off is when shooting with the camera mounted on a tripod (unless you want blur due to camera shake for some creative reason). In my seat-of-the pants estimation, VC enabled me to shoot sharp pictures handheld at 3-4 stops slower than I could have achieved without it, the one-stop performance range being due to specific shooting circumstances. This result is truly outstanding, and the VC system is tri-axial so it corrects for oblique camera shake as well as lateral and vertical camera movement. The system is utterly silent and, based on my shooting experience, completely dependable. Speaking of noise, the AF system is, if anything, somewhat quieter than average, and (on my Canons) commendably swift and decisive even though it’s not claimed to be “ultrasonic.” There’s also a little sliding-tab lock on the zoom ring that lets you secure it at the 17mm (most compact) position for transport or storage. It’s not really necessary, but it’s a detail sure to please nitpickers like me.

The Tamron 17-50mm f/2.8 VC comes with a flower-shaped lens hood that bayonets in reversed position over the front lens ring for stowage. It’s effective in minimizing flare at wide-angle-settings by preventing bright light from striking the front of the lens, but I must confess I seldom used it. The multi-coating on this lens is so efficient I was able to shoot against the light and in high-contrast lighting conditions with virtually no flare visible in any of my images. In terms of sharpness and contrast I found the performance of this lens to be exemplary at all apertures, focal lengths, and shooting distances, delivering crisp detail all the way to the extreme corners and edges of the frame. Distortion was likewise very low—under half a percent at the critical (for architecture) 17mm setting.

When subjected to the harshest possible test for chromatic aberration—shooting glossy white clapboard house siding on a bright, sunny day—the lens acquitted itself brilliantly, showing only a whiff of purplish fringing in white-line- edge areas of the image viewed at high magnification at the extreme borders and corners of the frame. For a fast-aperture zoom lens this is as good as it gets—and you’d probably have to make a 16x20 or larger print and view it from less than 10 inches away to see anything at all! In my professional opinion, the overall performance of this lens is truly outstanding, and fully merits the SP “ultra-high performance” designation.

Grab shot of pickup passing by an old hay storage house was taken at f/2.8 and 1/3200 sec. Wide f/2.8 aperture allowed a very fast shutter speed to freeze motion of truck even at ISO 100. Image quality wide open at the 17mm (26mm equivalent) focal length setting is outstanding.

Impromptu portrait was shot at f/2.8 and 1/160 sec, ISO 1600, 50mm (78mm equivalent) focal length setting. Note sharply rendered detail in eyelashes even at maximum aperture.

This brings me to an observation that could be critical for present and prospective Tamron 17-50mm f/2.8 VC users who want to get the best possible performance when shooting at wide apertures. The procedure that follows will assure that you will achieve exquisitely sharp images when shooting wide open at f/2.8 that equal or surpass those I’ve included here. What’s more, you will attain this very high level of performance with commendable consistency.

To cut to the chase, after analyzing hundreds of pictures I shot with the Tamron 17-50mm f/2.8 VC lens at wide apertures (that is f/2.8 or f/4) I discovered that occasional inconsistencies in sharpness were due to autofocus discrepancies, and not to any inherent optical performance deficits of the lens itself. In short, when I set the camera to multi-zone AF, it did not always focus precisely on my intended subject, but often locked onto some detail that was closer, and occasionally farther away. This phenomenon was more pronounced when shooting subjects closer than about 4 feet and I confirmed my findings by carefully assessing all parts of the captured image at high magnification. Examples: The portrait subject’s hair (bangs on the forehead) was extremely sharp, but the eyes were a tad soft, or, with flowers, the bloom (the main subject) was slightly soft, but adjacent buds were tack sharp. The simple remedy: Switch to central spot AF (which, on Canons, displays a red dot at the point of focus when AF is achieved) and auto-focus precisely on what you want crisply rendered in the final image. Locking focus on that critical detail by holding the shutter button partway in, then recomposing and shooting usually works too, but depth of field wide open at close distances is extremely shallow so you could still have a focusing discrepancy, especially if you move the camera too far from the original focus point before taking the picture. If this is the case, switch to manual focus and focus as critically as you can. The manual focus action on the 17-50mm is smooth and very precise, and with my cameras at least, achieving precise manual focus was quite easy, even in dim light (another advantage of the “bright” f/2.8 aperture).

My final point about the Tamron 17-50mm VC concerns its out-of-focus image quality, also known as bokeh. It is in a word, gorgeous—very natural looking with smooth transitions and excellent retention of the basic subject form, the hallmarks of good bokeh. One enthusiast reviewer described it as “creamy” which strikes me as just about right. If you’ve always hankered for a fast-aperture mid-range zoom of outstanding quality at a very reasonable price this one is certainly a top contender. Just make sure you’re not being sabotaged by your camera’s AF system and you’ll get all the outstanding performance this lens can deliver.