Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (Canon) - Review / Test Report
Lens Reviews - Canon EOS (APS-C)

Special thanks to Simon Procz for providing this lens!

Introduction

The Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF] (difficult to speak in one gasp ...) is the latest addition to the popular set of fast standard zooms. Tamron has categorized the 17-50mm as SP (Super Performance) lens - Tamron's professional grade product league. As indicated by the Di II the lens provides a reduced image circle so it is only compatible to APS-C DSLR. Its field-of-view is equivalent to ~27-80mm (1.6x crop) on full frame cameras. The lens is available in Canon, Nikon and Sony (KM) mount. At a price around 400€/US$ the Tamron costs only a fraction of the genuine manufacturer alternatives making it pretty attractive to budget shoppers who are looking for a good deal for their bucks.

The optical construction is made of 16 elements in 13 groups including two hybrid aspherical elements, one LD (Low Dispersion) glass element and one XR (Extra Refractive) element. According to Tamron the characteristic of the XR element allows a very compact design (82x74mm, 434g). Both the Canon EF-S 17-55mm f/2.8 USM IS and even more so the Nikkor AF-S 17-55mm f/2.8 ED are substantially bigger but the Sigma AF 18-50mm f/2.8 EX DC is pretty much comparable in size. The min. focus distance is 0.27m resulting is a max. object magnification of ~1:4.5 at 50mm. The lens features 7 circular aperture blades. The filter size is 67mm.

The build quality is very decent build quality but typical for most Tamron lenses there's a little too much plastic in there for my taste. Nonetheless it is still one of the better implementations in Tamron land. The zoom ring feels very smooth. Same goes for the focus ring which is even a little damped (are the old times coming back after all ?). On the downside Tamron still didn't manage to decouple the focus ring from the AF motor so the ring rotates during AF operations.
As you can see in the product shot above the lens extends when zooming towards the long end of the zoom range and the supplied petal-shaped hood adds a little extra length on top. Thanks to internal focusing the front element does not rotate so using a polarizer remains easily possible.
Due to a very short focus path (about 45 degrees) the slightly noisy AF is very fast. During the field tests the AF accuracy was fine in outdoor conditions but a little unsure indoors (low light) at the wide-end of the zoom range - the EOS 350D is no stellar performer here anyway though.




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