Tamron 17-50mm f/2.8 XR Di II

Tamron SP AF17-50mm F/2.8 XR Di-II LD ASPHERICAL [IF]

Model Name A16
Focal Length 17-50mm [same FOV as a 27-80 zoom would have on a full frame camera]
Maximum Aperture f2.8
Minimum Aperture f32
Angle of View 78° 45' - 31° 11' (APS-C size equivalent)
Lens Construction 16 elements in 13 groups
Minimum Focus Distance 0.27m (10.6") (Over the entire zoom range)
Maximum Mag. Ratio 1:4.5 (at f=50mm MFD 0.27m)
Filter Diameter 67mm
Overall Length 81.7mm (3.2") *
Maximum Diameter 74.0mm (2.9")
Weight 434 grams (15.3oz.) *
Diaphragm Blades 7 blades (Circular aperture)
Standard Accessory Flower-shaped Lens Hood
Compatible Mount Canon AF, Konica-Minolta AF-D, Nikon AF-D

The Tamron 17-50mm f/2.8 XR Di II Lens delivers very good image quality in a small, light, fast and affordable package. Add in the very popular focal length range and you have a lens that is just right for many digital SLR camera owners. The early-in-its-lifecycle popularity this lens is enjoying substantiates this claim.

Like Canon's EF-S Lenses, the Tamron 17-50mm f/2.8 XR Di II Lens is compatible only with "digital" SLRs - and only with the higher 1.5x/1.6x crop factor digital SLRs. Being sized for a smaller-format sensor allows a smaller design to be used. Measuring 2.9 x 3.2" (74 x 82mm)(d x l) and weighing 15.2 oz (430g), the Tamron 17-50 is an ideal size for the smaller digital SLR bodies. It balances and handles very nicely.

Build quality is not rugged, but it is solid - very adequate I'd say. The included hood is similarly built. The rubber on the zoom ring is grippy, soft and deeply ribbed. The zoom and focus rings turn smoothly. Tamron's rear lens cap only attaches at one position - a bit of a pain since I'm used to Canon's 3 attachment positions. Tamron's excellent center-pinch 67mm front cap more than makes up for this pain - I've considered putting these on my Canon lenses - And many of Sigma's lenses desperately need them.

The Tamron SP AF17-50mm F/2.8 XR Di-II LD Aspherical [IF] uses High Refractive Index glass (XR) to lower aberrations and make the lens more compact, Low Dispersion glass (LD) to minimize chromatic aberration and two Hybrid Aspherical Elements to further reduce residual aberrations and reduce the physical length of the lens.

On to more important issues ... The Tamron 17-50mm f/2.8 XR Di II Lens' AF is rather fast, but the high pitch buzz made by the focus motor is deceptive - making the lens sound slower. I found AF accuracy to be quite good with relatively few missed shots (that were not my fault at least). This is an internal-focusing lens - It does not change length during focusing and the front element does not rotate. FTM (Full Time Manual) focusing is not supported. Since the manual focus ring is rather small and in front of the larger focus ring, I did not find the focus ring turning during autofocusing to be much of a problem. It does turn though. The Tamron 17-50's minimum focus distance is 10.6" (0.27m) and provides a respectable .22x magnification factor. Both the zoom and focus rings rotate the opposite direction of Canon's lens rings. A zoom lock switch is provided.

The optical quality of the Tamron 17-50mm f/2.8 XR Di II Lens is excellent (especially for the price). I find my images sharp even when wide open at f/2.8 at all focal lengths - I do not hesitate to use this lens at f/2.8. Narrowing the aperture 1 stop or so yields slightly sharper image centers and noticeably better corners as the corners are somewhat soft wide open.

If the subject or background is an evenly-shaded solid color, you might notice slight vignetting when the lens is at f/2.8 at the wider focal lengths. Otherwise, vignetting will not be noticeable. Some CA (Chromatic Aberration) can be seen in real life shots, but nothing I would consider objectionable. Flare is very well controlled. Some barrel distortion is visible at the 17mm end. Pincushion distortion becomes visible at 24mm and more noticeable at 35mm before lessening to the 50mm end. Colors seem fine - neutral. The 7-blade aperture produces pleasant out-of-focus highlights.
In the Tamron 17-50mm f/2.8 XR Di II Lens, we have a very useful tool. Since it is small and light, we can take it everywhere. Since it is fast (f/2., we can use it in low light and indoors - and to stop action. Since it has very good image quality, we can use it for important shots. This list along with a nice general-purpose focal length range fills the requirements of a huge range of photographic opportunities (I'll let you think of them). Optically the Tamron SP AF17-50mm F/2.8 XR Di-II LD Aspherical [IF] is better than the Canon EF-S 17-85/4-5.6 IS, and though 1-2 stops faster, it lacks IS and the zoom range is smaller. I haven't yet had a chance to look at the Canon EF-S 17-55/2.8 IS USM, but at $1200 it would have to be really good to justify the price.
For the price, the Tamron 17-50 is a bargain lens.
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