This is not the only time I have purchased a non-Canon lens and this one was kind of a last minute purchase. One of the main reasons for buying a Tamron lens is that they are far cheaper than the equivalent Canon product and in my experience there is rarely any variance in quality. Perhaps the only drawback is that they tend to look a bit on the cheap side when you compare them with their Canon or Nikon equivalents, but for me this really is a minor point.
The Tamron SP AF 17-35mm is a superb ultra wide-angle zoom lens that starts at 17mm when used with a conventional 35mm SLR camera. When mounted on an APS-size digital SLR camera, it provides a focal length coverage equivalent to a 28-55mm (on a 35mm format camera), covering the desirable wide-angle to standard range. Image distortion, spherical, and other aberrations are corrected and reduced through the use of three large compound aspherical elements. This is to ensure high-definition photographs throughout the focal length. A major characteristic of many wide angle lenses are colour anomalies such as chromatic aberration and these have been diminished in this lens with the use of an LD element. This is a type of special glass that compensates for lateral aberration, and as such provides sharp and correctly coloured images even at the corners.
The photos I have managed to capture with this lens have been top quality with sharp images and plenty of detail. There is virtually no noticeable distortion even when taking shots close up to the subject. Images remain very sharp even at the wide angle range . The lens seems to perform well even wide open at 17 and 26mm. At 35mm it's probably not quite as sharp but this can be overcome by stopping down a little which will give you extra sharpness. When I tried it out is store I also found the speed of focus a little faster than the canon 17-40 f4. The pictures it takes are so good that if you can do without the zoom for the day then you can use it as a general walk-about lens.
One thing I like about this lens is that it is a very light lens which is surprising when you pick it up after first seeing it. The lens seems solidly constructed with a low reflectivity black finish and a rubberized zoom control. It comes with a "petal" style detachable lens hood that helps in the avoidance of unwanted flare. The barrel material appears to be plastic but it feels more than comfortable in the hand and compares well with my other Canon lenses. Focus can be switched between AF and MF with a small switch on the left, near the lens mount. The lens extends slightly (under 1cm) when zoomed, but does not change length when focusing. Although the front of the barrel does not rotate when the lens is zoomed or focused, the focus ring does rotate during autofocus, so it is important to keep your fingers out of the way.
In conclusion if you're looking for a fast, wide (17mm) lens, this Tamron option compares well with other top brand lenses and comes a lot cheaper than similar Canon or Nikon lenses.
At www.cameraworld.co.uk you'll find this lens priced at £327.99.
~~ Technical Summary ~~
Lens Construction (Groups/Elements) 11/14
Angle of View: 104°-63°
Type of Zooming Rotation
Diaphragm Blade Number 7
Maximum Aperture F/2.8-4
Minimum Focus 0.3m (11.8") (entire zoom range)
Macro Mag. Ratio: 1:5.4 (at 35mm)
Filter Diameter: 77mm
Weight 440g (14.4oz.)
Diameter x Length ø83.2mm x 86.5mm
Accessory Flower shaped lens hood
Mount: Canon, Minolta, Nikon-D, Pentax